Integrated optical circuit switching device and manufacturing method thereof

Abstract

The present disclosure relates to an optical switching network having optical switches that controllably reroute light between bus optical waveguides. An optical switch includes a shunt optical waveguide disposed vertically in a gap between a first bus optical waveguide formed in a first waveguide layer and a second bus optical waveguide formed in a second waveguide layer and configured to movably optically couple the first and second bus optical waveguides when activated. The first waveguide layer and the optical switch are formed on a first substrate and the second waveguide layer is formed on a second substrate bonded to the first substrate or mechanically supported by a plurality of anchors extending between the first and second substrates. The optical switch network includes a sensor for identifying a failed optical switch and a recovery optical waveguide and optical switch providing a recovery optical path to bypass the failed optical switch.

Description

Integrated optical circuit switching device and its manufacturing method

[0001] Incorporate by reference into any priority application

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 511427, filed June 30, 2023, entitled “Micro-Electro-Mechanical System Optical Circuit Switch Fabricated on Two Wafers,” and U.S. Provisional Patent Application No. 63 / 562179, filed March 6, 2024, entitled “Integrated Optical Circuit Switch Devices and Methods of Fabricating a Game,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to optical switches for routing optical signals in photonic systems and circuits, and more specifically, to integrated optical circuit switches including electromechanically actuated optical switches. Background Technology

[0004] Compared to electronic systems, performing data processing and transmission tasks in the optical domain can significantly improve data transmission and processing speeds. A crucial task in most computing or communication systems is controlling signal paths within a network of signal channels. Switching circuits can be included in reconfigurable interconnects that controllably transmit signals between different channels. Optical switching circuits, providing reconfigurable optical interconnects between multiple optical waveguides, are essential building blocks in most optical processing and communication systems, and their performance advantages can have a significant impact on these systems. Summary of the Invention

[0005] In some aspects, the technology described herein relates to an integrated optical circuit (IOC) comprising: a first waveguide layer in which a first bus optical waveguide is formed; a second waveguide layer in which a second bus optical waveguide is formed; an optical switch comprising a shunt waveguide vertically disposed in a gap between the first and second bus optical waveguide layers and configured to movably couple the first bus optical waveguide and the second bus optical waveguide when activated; and a pair of optical alignment structures formed in the first and second waveguide layers, wherein the optical alignment structures are optically aligned within a predetermined tolerance to correspondingly align the first and second waveguide layers and the optical switch within the predetermined tolerance, such that when activated, the shunt waveguide optically couples the first and second bus optical waveguides to redirect light therebetween.

[0006] In some aspects, the technology described herein relates to a method for aligning two wafers comprising an integrated photonic device, the method comprising: providing a first wafer comprising: a first waveguide layer wherein a first bus optical waveguide is formed; an optical switching structure comprising a shunt waveguide configured to movably optically couple the first bus optical waveguide to a second bus optical waveguide when activated to redirect light between the first and second bus optical waveguides; and a first of a pair of optical alignment structures comprising the first waveguide structure; providing a second wafer comprising: a second waveguide layer wherein the second bus optical waveguide is formed; and the pair of optical alignment structures. The second of the alignment structures includes a second waveguide structure; the first waveguide structure provides optical input power to the first of the pair of optical alignment structures; the second wafer is positioned relative to the first wafer such that the second waveguide structure is positioned above the first waveguide structure; the output optical power output from the second waveguide structure is measured as a result of the optical coupling between the first and second waveguide structures; the first wafer is aligned relative to the second wafer based on the measured output optical power; and wherein, when the optical switching structure is activated, the measured output optical power is directly related to the optical coupling strength between the first and second optical waveguides.

[0007] In some aspects, the technology described herein relates to an integrated optical circuit (IOC) comprising: a first waveguide layer in which a first bus optical waveguide is formed; a second waveguide layer in which a second bus optical waveguide is formed; an optical switch comprising a shunt waveguide vertically disposed in a gap between the first and second bus optical waveguide layers and configured to movably couple the first bus optical waveguide and the second bus optical waveguide when activated; and a pair of physical alignment structures formed on the first and second waveguide layers, wherein the physical alignment structures are physically coupled to align the first and second waveguide layers and the optical switch within a predetermined tolerance, such that when activated, the shunt waveguide optically couples the first and second bus optical waveguides to redirect light therebetween.

[0008] In some aspects, the technology described herein relates to a method for aligning two wafers comprising an integrated photonic device, the method comprising: providing a first wafer comprising: a first waveguide layer wherein a first bus optical waveguide is formed; an optical switch structure comprising a shunt waveguide configured to movably optically couple the first bus optical waveguide to a second bus optical waveguide when activated to redirect light between the first and second bus optical waveguides; and a first physical alignment structure in a pair of physical alignment structures; providing a second wafer comprising: a second waveguide layer wherein a second bus optical waveguide is formed; and a second physical alignment structure in the pair of physical alignment structures, the second physical alignment structure being configured to physically couple to the first physical alignment structure; laterally aligning the first and second wafers to align the first physical alignment structure above the second physical alignment structure within a predetermined tolerance; and vertically joining the first and second physical alignment structures such that, when activated, the shunt waveguide optically couples the first and second bus optical waveguides to redirect light therebetween.

[0009] In some aspects, the technology described herein relates to a method for aligning two wafers comprising an integrated photonic device, the method comprising: providing a first wafer comprising: a first waveguide layer wherein a first bus optical waveguide is formed; an optical switch structure comprising a shunt waveguide configured to movably optically couple the first bus optical waveguide to a second bus optical waveguide when activated to redirect light between the first and second bus optical waveguides; and a first physical alignment structure in a pair of physical alignment structures; providing a second wafer comprising: a second waveguide layer wherein a second bus optical waveguide is formed; and a second physical alignment structure in the pair of physical alignment structures, the second physical alignment structure being configured to physically couple to the first physical alignment structure; providing microbeads between the first and second physical alignment structures to mechanically link the first and second physical alignment structures; laterally aligning the first and second wafers to align the first physical alignment structure above the second physical alignment structure within a predetermined tolerance; and vertically joining the first and second physical alignment structures via the microbeads such that, when activated, the shunt waveguide optically couples the first and second bus optical waveguides to redirect light therebetween.

[0010] In some aspects, the technology described herein relates to an integrated optical circuit (IOC) comprising: a first waveguide layer formed on a substrate, wherein a first bus optical waveguide is formed therein; a second waveguide layer wherein a second bus optical waveguide is formed; an optical switch comprising a shunt waveguide vertically disposed in a gap between the first and second bus optical waveguide layers and configured to movably optically couple the first and second bus optical waveguides when activated to redirect light between the first and second bus optical waveguides; and a plurality of vertical paths acting as mechanical anchors and electrical connections between the first and second waveguide layers to securely suspend the second waveguide layer above the first waveguide layer, the vertical paths being formed of a material selectively etched with sacrificial material removed from the gap during manufacturing.

[0011] In some aspects, the technology described herein relates to a method of manufacturing an integrated optical circuit (IOC) device, the method comprising: manufacturing a first wafer including: photolithographically patterning to form a first bus optical waveguide extending within a first waveguide layer on a front side of a first substrate, and forming an optical switch structure on the first substrate including a shunt waveguide at least partially fixedly buried in a sacrificial material; manufacturing a second wafer including a second optical bus waveguide photolithographically patterned to form a second waveguide layer extending within a second waveguide layer on a front side of a second substrate; bonding the front surface of the second wafer to the front surface of the first wafer; removing the second substrate; forming a plurality of vertical pathways through the second waveguide layer and further through the sacrificial material, the vertical pathways acting as mechanical anchors and electrical connections between the first and second waveguide layers; selectively removing the sacrificial material to release the shunt waveguide to configure the shunt waveguide to movably optically couple the first bus optical waveguide and the second bus optical waveguide when activated to redirect light between the first and second bus optical waveguides.

[0012] In some aspects, the technology described herein relates to an integrated optical circuit (IOC) device comprising: a first waveguide layer formed on a first substrate, wherein a first bus optical waveguide is formed therein; a second waveguide layer formed on a second substrate, wherein a second bus optical waveguide is formed therein; an optical switch comprising a shunt waveguide vertically disposed in a gap between the first and second bus optical waveguide layers and configured to movably optically couple the first and second bus optical waveguides to redirect light between the first and second bus optical waveguides when activated; and a plurality of mechanical stops extending vertically between a first and a second wafer, wherein each mechanical stop has a first mechanical stop portion formed on the first substrate and a second mechanical stop portion formed on the second substrate, wherein the second wafer is bonded to the first wafer using the mechanical stops such that the first and second bus optical waveguides are vertically separated by a distance defined by the mechanical stops.

[0013] In some aspects, the technology described herein relates to a method of manufacturing an integrated optical circuit switching (OCS) device having at least one optical switching unit, the method comprising: manufacturing a first wafer comprising: photolithographically patterning a first bus optical waveguide extending within a first waveguide layer on a front side of a first substrate, and forming an optical switching structure on the first substrate comprising a shunt waveguide at least partially fixedly buried in a sacrificial material; manufacturing a second wafer comprising a second optical bus waveguide extending within a second waveguide layer on a front side of a second substrate; and forming a plurality of mechanical stops, each having formed in A first portion on the first substrate and a second portion formed on the second substrate; selective removal of the sacrificial material to release the shunt waveguide; bonding the second wafer to the first wafer by contacting at least the first portion of the mechanical stop with a corresponding second portion of the mechanical stop, such that the first bus optical waveguide and the second bus optical waveguide are vertically separated by a distance defined by the mechanical stop, and such that the shunt waveguide is configured to movably optically couple the first bus optical waveguide and the second bus optical waveguide when activated to redirect light between the first and second bus optical waveguides.

[0014] In some aspects, the technology described herein relates to an optical switching unit comprising: a first waveguide layer in which a first bus optical waveguide is formed; a second waveguide layer in which a second bus optical waveguide is formed; an optical switch comprising a shunt waveguide disposed in a vertical gap between the first and second bus optical waveguide layers and configured to movably couple the first bus optical waveguide and the second bus optical waveguide when activated; and one or more microelectromechanical system (MEMS) actuators configured to mechanically move one or both end regions of the shunt waveguide when activated to cause optical coupling between the first bus optical waveguide and the second bus optical waveguide.

[0015] In some aspects, the technology described herein relates to an integrated optical circuit comprising: a first plurality of bus optical waveguides formed over a substrate and terminated with a first plurality of optical ports; a second plurality of bus optical waveguides formed over the substrate; a plurality of optical switches including a plurality of shunt optical waveguides configured to redirect light between individual optical bus waveguides in the first plurality of bus optical waveguides and individual optical bus waveguides in the second plurality of bus optical waveguides when activated by an activation signal; and a plurality of sensors disposed on the substrate and configured to generate a plurality of sensor signals indicating the on and off states of the plurality of optical switches.

[0016] In some aspects, the technology described herein relates to an integrated optical circuit comprising: a first bus optical waveguide formed over a substrate; a second bus optical waveguide formed over the substrate; a recovery waveguide formed over the substrate; a primary optical switch comprising a first shunt optical waveguide configured to movably optically couple the first bus optical waveguide and the second bus optical waveguide when activated by a first activation signal to redirect light between the first and second bus optical waveguides; a first recovery optical switch comprising a second shunt optical waveguide configured to movably optically couple the first bus optical waveguide and the recovery waveguide when activated by a second activation signal to redirect light between a segment of the first bus optical waveguide and the recovery waveguide; and a second recovery optical switch comprising a third shunt optical waveguide configured to movably optically couple the second bus optical waveguide and the recovery waveguide when activated by a second activation signal to redirect light between a segment of the second bus optical waveguide and the recovery waveguide, wherein the recovery waveguide is configured to couple the first and second bus optical waveguides when the second and third optical switches are activated.

[0017] In some aspects, the technology described herein relates to an integrated optical circuit comprising: a first plurality of optical waveguides extending longitudinally on a substrate and terminating near an edge of the substrate; and a second edge optical coupler formed on the substrate and configured to couple fiber optics to the first optical waveguide among the first plurality of optical waveguides, the first edge optical coupler comprising a tapered waveguide extending longitudinally from an end of the first optical waveguide to the edge of the substrate, wherein the lateral width of the tapered waveguide decreases from the end of the first optical waveguide to the edge of the substrate, and wherein a region of the substrate below the tapered waveguide is removed to form a slit below the tapered waveguide.

[0018] In some aspects, the technology described herein relates to an edge coupler interposer layer comprising: a first waveguide facet array located at a first periodic position, a first longitudinal position, and a common vertical position along a lateral direction; and second and third waveguide facet arrays located at a second longitudinal position, wherein the second and third waveguide facet arrays are vertically separated and form a vertically separated waveguide facet array at the second periodic position along the lateral direction, wherein the first lateral pitch of the first waveguide facet array is smaller than the second lateral pitch of the second waveguide facet array; wherein the first and second waveguide facets in the first waveguide facet array are optically coupled to different waveguide facets of the vertically separated waveguide facet array. Attached Figure Description

[0019] Figure 1 schematically illustrates an optical switching network comprising multiple optical waveguides controllably interconnected using multiple switching units.

[0020] Figure 2A is a schematic top view illustrating an example integrated optical circuit switch (IOCS) device, which includes an optical switch matrix and two groups of bus optical waveguides optically connected to optical ports at the edge of the IOCS device.

[0021] Figure 2B schematically illustrates a top view of an exemplary IOCS device, which includes an optical switch matrix and two groups of bus optical waveguides optically connected to optical ports at opposite edges of the IOCS device.

[0022] Figure 2C schematically illustrates a top view of an exemplary IOCS device, which includes an optical switch matrix and two groups of bus optical waveguides connected to a group of optical ports at the edge of the IOCS device.

[0023] Figure 2D schematically illustrates a top view of an exemplary IOCS device, which includes an optical switch matrix and two groups of bus optical waveguides connected to optical ports at opposite edges of the IOCS device.

[0024] Figure 3A schematically illustrates a top view and two cross-sectional side views of an example optical switching unit of the IOCS device shown in Figures 2A to 2D in the off state.

[0025] Figures 3B to 3C schematically illustrate the end region of the shunt waveguide of the optical switching unit shown in Figure 3A, as well as a close-up view of the corresponding microelectromechanical system (MEMS) actuator and flexible support structure.

[0026] Figure 4 schematically illustrates a top view and two cross-sectional side views of the optical switching unit shown in Figure 3A in the ON state.

[0027] Figure 5A schematically illustrates the vertical cross-sectional side view of the optical switching unit shown in Figure 3A along the curved section A'A, which shows the corresponding parts of the MEMS actuator for the bus optical waveguide, the shunt waveguide, and the end region of the control shunt waveguide.

[0028] Figure 5B schematically illustrates the end region of the shunt waveguide of the optical switching unit shown in Figure 5B and a close-up view of the corresponding MEMS actuator.

[0029] Figures 6A and 6B schematically illustrate two cross-sectional side views of a single switching unit of an exemplary IOCS device according to the first embodiment described herein. The two cross-sectional side views are rotated 90 degrees relative to each other.

[0030] Figure 6C is a flowchart of an exemplary process for manufacturing the IOCS device shown in Figures 6A to 6B, according to some embodiments disclosed herein.

[0031] Figures 7A and 7B schematically illustrate two cross-sectional side views of a single switching unit of an exemplary IOCS device according to the second embodiment described herein. The two cross-sectional side views are rotated 90 degrees relative to each other.

[0032] Figure 7C is a flowchart of an exemplary process for manufacturing the IOCS device shown in Figures 7A to 7B, according to some embodiments disclosed herein.

[0033] Figures 8A and 8B schematically illustrate top views of a first and second substrate for fabricating an exemplary IOCS device, the IOCS device having an optical port formed on the second substrate and an interlayer coupler that optically connects a bus optical waveguide of the first substrate to the optical port of the second substrate.

[0034] Figures 8C to 8D schematically illustrate two cross-sectional side views of an exemplary IOCS formed using the first and second substrates shown in Figures 8A to 8B. The two cross-sectional side views are rotated 90 degrees relative to each other.

[0035] Figures 9A and 9B schematically illustrate top views of a first and second substrate for fabricating an exemplary IOCS device, the IOCS device having an optical port formed on the first substrate and an interlayer coupler that optically connects a bus optical waveguide of the second substrate to the optical port on the first substrate.

[0036] Figures 9C to 9D schematically illustrate two cross-sectional side views of an exemplary IOCS formed using the first and second substrates shown in Figures 9A to 9B. The two cross-sectional side views are rotated 90 degrees relative to each other.

[0037] Figures 10A to 10B schematically illustrate top views of a first (A) and a second (B) substrate for fabricating an exemplary IOCS device. The IOCS device has a first group of optical ports formed on the first substrate and a second group of optical ports formed on the second substrate. Each group of optical ports is connected to a waveguide on the corresponding substrate without any interlayer couplers.

[0038] Figures 10C to 10D schematically illustrate two cross-sectional side views of an exemplary IOCS formed using the first and second substrates shown in Figures 10A to 10B. The two cross-sectional side views are rotated 90 degrees relative to each other.

[0039] Figures 11A to 11C schematically illustrate the top view (A), side view (B), and perspective view (C) of an exemplary tapered waveguide interlayer coupler.

[0040] Figures 12A to 12B schematically illustrate top views of a first substrate (A) or wafer including a first portion of an active alignment structure and a second substrate (B) or wafer including a second portion of an active alignment structure.

[0041] Figure 12C schematically illustrates a perspective top view of an IOCS device formed by overlapping first and second substrates or wafers when active alignment structures on two wafers are aligned to increase or maximize the optical power transmitted via one or more pairs of active alignment structures.

[0042] Figures 13A to 13C schematically illustrate perspective views of three pairs of substrates (or wafers) having self-aligned structures including protrusions and openings of different shapes.

[0043] Figures 13D to 13F schematically illustrate perspective top views of the three pairs of substrates shown in Figures 13A to 13C when the two substrates of each pair overlap and the self-aligned structures on the first and second substrates are partially joined.

[0044] Figures 13G and 13H schematically illustrate the near-cross-sectional side views of the alignment structure of the substrate pair shown in Figures 13A and 13C, respectively, when the two substrates of each pair overlap and the self-aligned structures on the first and second substrates are partially joined.

[0045] Figures 14A to 14C schematically illustrate perspective views of three pairs of substrates (or wafers) having a self-aligned structure including openings (or holes) of different shapes, wherein the openings on the first substrate are configured to be mechanically coupled to openings on the second substrate via microbeads.

[0046] Figures 14D to 14F schematically illustrate perspective top views of the three pairs of substrates shown in Figures 14A to 14C, when the two substrates of each pair overlap and portions of the self-aligned structures on the first and second substrates are mechanically coupled via microbeads.

[0047] Figure 14G schematically illustrates a near-cross-sectional side view of the alignment structure of any of the three pairs of substrates shown in Figures 14A to 14C when the two substrates of each pair overlap and portions of the self-aligned structure on the first and second substrates are mechanically coupled by microbeads.

[0048] Figure 15A schematically illustrates a perspective view of a pair of substrates (or wafers) having a self-aligned structure including cylindrical protrusions and holes.

[0049] Figure 15B schematically illustrates a perspective top view of the substrate pair shown in Figure 15A when the two substrates overlap and the self-aligned structures on the first and second substrates are joined.

[0050] Figure 15C schematically illustrates a side-view myopic cross-sectional view of a pair of aligned structures of the substrate pair shown in Figure 15B.

[0051] Figure 16A schematically illustrates a perspective view of a pair of substrates (or wafers) having a self-aligned structure including cubic or rectangular protrusions and holes.

[0052] Figure 16B schematically illustrates a perspective top view of the substrate pair shown in Figure 16A when the two substrates overlap and the self-aligned structures on the first and second substrates are joined.

[0053] Figure 16C schematically illustrates a side view of a near-cross section of a pair of aligned structures of the substrate pair shown in Figure 16B.

[0054] Figure 17A schematically illustrates a top view of an example integrated optical circuit switch (IOCS) device similar to the device shown in Figure 2A, the IOCS device having a tap coupler and a photodiode for monitoring the optical power rerouted from the optical switch to the optical port.

[0055] Figure 17B schematically illustrates a top view of an exemplary IOCS device similar to the device shown in Figure 2A, the IOCS device having a photodiode for monitoring the optical power rerouted from the optical switch to the optical port and the optical power through the switching unit.

[0056] Figure 17C schematically illustrates a top view of an exemplary IOCS device similar to the one shown in Figure 2A, the IOCS device having an in-line photodiode for monitoring the optical power rerouted from the optical switch to the optical port.

[0057] Figure 18 schematically illustrates a top view of an example IOCS device similar to the device shown in Figure 2A, the IOCS device having an optical switch with an integrated capacitive sensor for monitoring the state of the optical switch.

[0058] Figure 19A is a schematic top view illustrating an exemplary IOCS device having two bus optical waveguides, a primary optical switch, a recovery optical waveguide, and a recovery optical switch for bypassing the primary optical switch.

[0059] Figure 19B schematically illustrates a top view of an exemplary IOCS device having a recovery optical waveguide formed in a single waveguide layer and a recovery optical switch for establishing a recovery optical path via the recovery optical waveguide.

[0060] Figure 20A is a schematic top view illustrating an exemplary IOCS device having a recovery optical waveguide formed in two waveguide layers and a recovery optical switch for establishing a recovery optical path via the recovery optical waveguide.

[0061] Figures 20B to 20C are schematic top views of the first wafer or waveguide layer (20B) and the second wafer or waveguide layer (20C) of the IOCS device shown in Figure 20A.

[0062] Figures 21A and 21B schematically illustrate a front view (21A) and a three-dimensional view (21B) of an exemplary optical edge coupler used to couple an optical fiber waveguide to a waveguide on a chip.

[0063] Figures 21C to 21D schematically illustrate a front view (21C) and a three-dimensional view (21C) of another example optical edge coupler used to couple an optical fiber waveguide to a waveguide on a chip.

[0064] Figures 21E to 21F schematically illustrate a front view (21E) and a three-dimensional view (21F) of another example optical edge coupler used to couple an optical fiber waveguide to a waveguide on a chip.

[0065] Figures 22A and 22B schematically illustrate the front view (22A) and three-dimensional view (22B) of the edge coupler interlayer configured to optically couple a one-dimensional (1D) array of optical ports along the edge of a photonic chip to a two-dimensional (2D) array of optical ports.

[0066] Figure 22C schematically illustrates a top view of an IOCS device having two sets of optical ports along two different edges of the IOCS device and two edge coupler intermediary layers, each edge coupler intermediary layer being aligned and optically coupled to a set of optical ports. Detailed Implementation

[0067] Compared to operations in the electrical domain, signal operations in the optical domain can significantly increase bandwidth and reduce losses during data processing and transmission. Therefore, performing at least a portion of the data processing and transmission tasks required in an application in the optical domain can be advantageous. A crucial task in any computing or communication operation is controlling the signal paths within a network of signal channels. In many applications, this task is performed by switching circuitry comprising multiple reconfigurable interconnections between signal channels. Optical switching networks and circuits are modules that provide reconfigurable optical interconnections between multiple optical channels (e.g., optical waveguides) and can replace their electrical counterparts when performing data processing and transmission in the optical domain. Such optical switching modules may include multiple optical interconnect switching units, each configured to control the optical signal flow between at least two individual optical channels of the module. Optical switching networks and circuits can have significantly lower power requirements than electrical switching networks and circuits.

[0068] In some embodiments, optical switching units (also referred to as switching units) can be used to form a network of controllable optical interconnects between optical waveguides. In some embodiments, the optical waveguides can be formed into a matrix structure or arrangement comprising a first array of optical waveguides (e.g., horizontal waveguides) and a second array of optical waveguides (e.g., vertical waveguides) to form a matrix of waveguide crossings. In some embodiments, a waveguide crossing may include overlapping portions of the waveguides of the first array of optical waveguides and the waveguides of the second array of optical waveguides. In some embodiments, optical switches can be used to reconfigure optical transmission through the waveguide crossings. Reconfigurable waveguide crossings allow light propagating in one waveguide to be controllably coupled to the other waveguide of the waveguide crossing.

[0069] The switching unit may be a reconfigurable optical waveguide crossover comprising at least one pair of fixed-position bus optical waveguides of an optical network and an optical switch including a movable optical waveguide portion (e.g., a shunt waveguide), the movable optical waveguide portion being optically coupled and decoupled from each of the bus optical waveguides in the bus optical waveguide pair by controlled actuation (e.g., electromechanical actuation). In such a case, the first bus optical waveguide in the bus optical waveguide pair provides optical connection between a first and a second optical port of the optical network, and the second bus optical waveguide in the bus optical waveguide pair provides optical connection between a third and a fourth optical port of the optical network. The bus optical waveguides may cross each other at the crossover area, such that when the optical switch is in its on state, the shunt waveguide optically connects the first optical port to the third optical port and optically disconnects the first optical port from the second optical port by coupling light from the first bus optical waveguide to the second bus optical waveguide. In some embodiments, the shunt waveguide may include a curved (e.g., L-shaped) waveguide configured to couple light from one bus waveguide to another bus waveguide via two coupling regions of the shunt waveguide. Each coupling region may be located close to the end of the shunt waveguide and may be configured to couple light from the bus waveguide to the shunt waveguide when the optical switch is in the ON state (e.g., when mechanically actuated).

[0070] U.S. Patent No. 10,061,085, issued August 28, 2018, discusses examples of optical waveguide networks including switching units with optical switches, the entire contents of which are hereby incorporated by reference. It should be understood that if anything incorporated herein by reference is interpreted in any way as contradicting the corresponding content of this disclosure, this disclosure shall prevail.

[0071] Some existing optical switch networks are implemented based on optical switch and optical waveguide configurations fabricated on a single substrate, where bus optical waveguides are formed on a single waveguide layer. When the two bus optical waveguides of an optical switch network are within the same waveguide layer (e.g., fabricated through the same layer on a patterned substrate), the two bus optical waveguides physically cross each other at waveguide crossovers. Optical switches are positioned at these crossovers to controllably reroute light between the two bus optical waveguides. Given that the two bus optical waveguides should be optically isolated when the optical switches are off, the waveguide crossovers should be designed such that when light propagates in one of the two bus optical waveguides, it can pass through the waveguide crossover without leakage or coupling to the other bus optical waveguide. Additionally, the waveguide crossovers should support low-loss transmission via each of the bus optical waveguides. Designing waveguide crossovers that meet these conditions can be a challenging task; therefore, optical switch networks with bus optical waveguides in a single waveguide layer can suffer from poor performance due to one or both of high insertion loss or high optical crosstalk at individual waveguide crossovers. Given that optical switching circuits can contain a large number of switching units and thus a large number of waveguide crossings, even low levels of optical insertion loss and optical crosstalk at individual switching units can lead to significant loss of a single optical channel of the optical switching network (which passes through multiple switching units) and light leakage to all waveguides that cross the optical channel.

[0072] One solution to the aforementioned problem is to fabricate two bus optical waveguides on two vertically separated waveguide layers, which should be controllably connected via an optical switch. Using this method, one bus optical waveguide can cross over the other while the two waveguides remain optically isolated. Optical switching between such bus optical waveguides can be achieved using an optical switch configured to controllably couple the two vertically separated optical waveguides. However, integrating the optical switch (specifically, a microelectromechanical system (MEMS) optical switch) with this two-layer structure is not trivial, as the waveguide segments and MEMS actuators contain moving parts that should be released to activate the optical switch.

[0073] This disclosure describes structures, designs, and methods for fabricating integrated optical switches and networks comprising optical switching units formed of bus optical waveguides, wherein the bus optical waveguides are vertically separated from each other and controllably coupled by MEMS optical switches configured to reroute light between the bus optical waveguides.

[0074] The disclosed design and structure can be used to manufacture optical switches and optical switching units with lower optical crosstalk (in the off state) and lower optical insertion loss compared to existing optical switches and optical switching units. The improved performance of the disclosed optical switch is partly a result of using methods capable of manufacturing optical switching units with vertically separated bus optical waveguides and microelectromechanically activated optical switches. Furthermore, the manufacturing method described herein reduces the cost and complexity of two-layer optical switching circuits and facilitates the mass production of reliable and high-performance integrated optical circuit switches.

[0075] The disclosed optical switches and switching units can be manufactured using fabrication techniques for manufacturing complementary metal-oxide-semiconductor (CMOS) device structures. Therefore, in some embodiments, these optical switches and switching units can be directly fabricated on a silicon chip by utilizing the capabilities of a CMOS foundry, and in some implementations, they are at least partially co-fabricated on a common chip with the CMOS device and electronic circuitry (e.g., control circuitry for controlling the optical switches).

[0076] The disclosed optical switching circuit and corresponding optical switching unit can be used in various applications, including (but not limited to) communications, data centers, high-performance computing (HPC) and artificial intelligence (AI) and machine learning (ML) AI / ML systems and other applications.

[0077] Figure 1 schematically illustrates an example optical switching network (OSN) 100 with a matrix architecture. OSN 100 includes a first plurality of bus optical waveguides 102 that are matrix-controllably interconnected to a second plurality of bus optical waveguides 104 using switching units (SC1, SC2... and SC12). When all switching units are in the off state, the first plurality of bus optical waveguides 102 optically connect a first plurality of optical ports 106 to a second plurality of optical ports 108, and the second plurality of bus optical waveguides 104 optically connect a third plurality of optical ports 112 to a fourth plurality of optical ports 113.

[0078] In the illustrated example, for illustrative purposes, the first plurality of bus optical waveguides 102 comprises four waveguides, the second plurality of optical waveguides 104 comprises three waveguides, and the matrix of switching units comprises twelve switching units SC1 to SC12. In some embodiments, each switching unit provides controllable optical coupling between an individual waveguide in the first plurality of bus optical waveguides 102 and an individual waveguide in the second plurality of bus optical waveguides 104. In some embodiments, an individual switching unit may include at least one optical switch configured to optically couple one waveguide in the first plurality of bus optical waveguides 102 to one waveguide in the second plurality of bus optical waveguides 104. For example, when a switching unit is in the ON state, the optical switching unit of the switching unit may reroute an optical signal received from one port of the first plurality of optical ports 106 to one port of the third plurality of optical ports 112, or vice versa. In some such embodiments, when a switching unit is in the ON state, the same optical switch may not reroute an optical signal received from one port of the second plurality of optical ports 108 to one port of the third plurality of optical ports 112 or the fourth plurality of optical ports 113. In some embodiments, individual switching units may include two optical switches configured to controllably couple one optical waveguide of a first plurality of waveguides 102 to an optical waveguide of a second plurality of waveguides 104. In some such embodiments, when the two optical switches of the switching unit are in the ON state, an optical signal received from one of the first plurality of optical ports 106 is rerouted to one of the third plurality of optical ports 112, or vice versa, an optical signal received from one of the second plurality of optical ports 108 is rerouted to one of the third plurality of optical ports 112 (or vice versa) or one of the fourth plurality of optical ports 113.

[0079] In some embodiments, the OSN may be implemented based on an integrated photonic circuit (IPC) comprising bus optical waveguides and optical switches fabricated on one or more substrates. In some embodiments, the fabrication of the optical switches and / or bus optical waveguides may include monolithic fabrication and wafer-level integration (WSI). In some embodiments, the switching unit may include portions of two bus optical waveguides and one or more optical switches configured to controllably couple optical signals from one bus optical waveguide to the other. In some embodiments, the optical switches may include microelectromechanical systems (MEMS) optical switches.

[0080] As described herein, MEMS switches, MEMS optical switches, or MEMS actuators may include switches, optical switches, or actuators that are microelectromechanical systems (MEMS) or may include one or more MEMS features. For example, a MEMS switch, MEMS optical switch, or MEMS actuator may include design, structure, and / or activation mechanisms for use in a microelectromechanical system (MEMS). Thus, a MEMS-based optical switch or a MEMS-based actuator may also be referred to as a MEMS switch, MEMS optical switch, or MEMS actuator. A microelectromechanical system may include a microscopic device incorporating electronic components, moving parts, and actuators configured to electronically activate or move the moving parts.

[0081] In some embodiments, individual switching units (SC1, SC2... or SC12) of OSN 100 may include an optical switch located near a crossover region where a first bus optical waveguide in a first plurality of bus optical waveguides 102 intersects a second bus optical waveguide in a plurality of bus optical waveguides 104, and segments of the first and second bus optical waveguides associated with the crossover region. The optical switch may be configured to optically couple the first and second optical bus waveguides in an ON state and to allow light to propagate substantially continuously via the first and second bus optical waveguides in an OFF state. For example, when the optical switch of the SC is OFF, light supplied to a corresponding optical port in a first plurality of optical ports 106 may be transmitted via the SC to a corresponding optical port in a second plurality of optical ports 108. However, when the optical switch of the SC is ON, light supplied to an optical port may be transmitted by the optical switch to a corresponding optical port in a third plurality of optical ports 112. In some implementations, the SC may include a shunt waveguide and an actuator (e.g., a microelectromechanical actuator) configured to controllably couple the shunt waveguide to two bus optical waveguides associated with the SC.

[0082] This disclosure provides an OSN based on microelectromechanical systems (MEMS) technology, including an integrated optical circuit switching (IOCS) device. Some embodiments and methods disclosed herein provide an IOCS device including a first wafer (or substrate) bonded to a second wafer (or substrate). For example, OSN 100 may include this IOCS device formed by bonding two wafers (or substrates). In some embodiments, at least one of the first and second wafers may include an integrated photonic circuit (IPC). In some embodiments, at least one of the first and second wafers may include a microfabrication structure. In some embodiments, the first wafer may include optical switches for a first plurality of bus optical waveguides 102 and switching units (SC1, SC2... and SC12), and the first wafer may include a second plurality of bus optical waveguides 104. In some embodiments, the IOCS device may be fabricated by aligning and bonding (e.g., flip-chip bonding) the first and second wafers to form an SC network, which may controllably couple individual bus optical waveguides in the first plurality of bus optical waveguides 102 to individual bus optical waveguides in the second plurality of bus optical waveguides 104. In some embodiments, the actuators and shunt waveguides of the first wafer may be substantially fully fabricated and even fully functional prior to bonding. For example, the shunt waveguides and / or actuators may be released to allow their mechanical movement. In some other embodiments, the fabrication steps of the actuators and / or shunt waveguides (e.g., releasing the corresponding MEMS actuators and / or suspending the shunt waveguides) may be performed after the first wafer is bonded to the second wafer. In some such embodiments, after bonding the first and second wafers and before completing the fabrication of the optical switches and / or shunt waveguides, the substrate or layers of the second wafer may be removed (e.g., stripped) from the waveguide layers including the second plurality of bus optical waveguides 104.

[0083] Integrated optical switching network

[0084] Figure 2A shows a top view of an exemplary IOCS device 200 having first and third plurality of optical ports 106, 112 and first and second plurality of bus optical waveguides 102, 104. In some embodiments, the first and second plurality of waveguides 102, 104 are vertically separated and optically isolated. In some embodiments, the first plurality of waveguides 102 may be disposed on a first wafer and the second plurality of waveguides 104 may be disposed on a layer (e.g., substrate, wafer, or buffer layer) that is vertically separated from and / or at least partially suspended above the wafer. In some embodiments, the first plurality of waveguides 102 extend in a first direction and the second plurality of waveguides 104 extend in a second direction that is different from or intersects with the first direction. Thus, individual waveguides in the first (or second) plurality of waveguides are associated with multiple cross regions that intersect above or below individual waveguides in the second (or first) plurality of waveguides. Without an optical switch, the two waveguides are optically isolated through the cross regions. In some embodiments, an optical switch 207 may be disposed at or near the cross regions to form an optical switching unit (SC) 208. Optical switch 207 may be configured to optically couple a waveguide through a crossover region (or optical switching unit) when actuated. In some embodiments, optical switch 207 may include a shunt optical waveguide (also referred to as a shunt waveguide) located at or near the crossover region and a section of a bus optical waveguide associated with the crossover region. The shunt waveguide may include a short waveguide section extending from a first end to a second end (both located in SC 208). Optical switch 207 may further include an actuator (e.g., a microelectromechanical system actuator or a MEMS actuator) configured to move an end region of the shunt waveguide toward the first or second waveguide upon actuation to optically couple the end region to the first or second waveguide. In some embodiments, optical switch 207 may include two actuators (e.g., microelectromechanical system actuators or MEMS actuators) configured to move the first and second end regions of the shunt waveguide toward the first and second waveguides, respectively (upon actuation), to optically couple the first and second waveguides. In some implementations, the MEMS actuator, shunt waveguide, and first waveguide may be fabricated on a common wafer or substrate.

[0085] In some embodiments, optical ports labeled “A1”, “A2”...“Am” are connected and optically communicate with bus optical waveguides in the first plurality of bus optical waveguides 102, and optical ports labeled “B1”, “B2”...“Bm” are connected and optically communicate with bus optical waveguides in the second plurality of bus optical waveguides 104. In some embodiments, individual optical ports in the first or third plurality of optical ports 106, 112 may be connected to a first end corresponding to a bus optical waveguide (also referred to as a bus waveguide) and may be used bidirectionally as optical input (e.g., for receiving light from an optical fiber, device, or optical waveguide on another PIC) and optical output (e.g., for transmitting light to an optical fiber, device, or optical waveguide on another PIC). In some embodiments, a second end of an individual waveguide may be optically communicated with another optical device or waveguide (e.g., an optical waveguide outside the IOCS device 200) and may be configured to transmit light to and / or receive light from the optical device or waveguide. In some embodiments, another optical device or waveguide may be fabricated on the same chip, wafer, or substrate on which a first plurality of waveguides 102 or a second plurality of waveguides 104 are fabricated. In some embodiments, another optical device or waveguide may be fabricated on a separate chip, wafer, or substrate, mounted on a carrier chip on which a wafer, chip, or substrate containing the first plurality of waveguides 102 or the second plurality of waveguides 104 is mounted.

[0086] In some embodiments, an IOCS device may include a first plurality of waveguides 102 extending from a first plurality of optical ports 106 to a second plurality of optical ports 108 and a second plurality of waveguides 104 extending from a third plurality of optical ports 112 to a fourth plurality of optical ports 113. An example of such an embodiment is the IOCS device 201 shown in FIG. 2B. The IOCS device 201 includes four sets of input / output optical ports, labeled “A1”, “A2”...“Am”, “B1”, “B2”...“Bn”, “C1”, “C2”...“Cm” and “D1”, “D2”...“Dn”. In some embodiments, these optical ports may be referred to as “input”, “output”, “fall-down”, “through”, and “add” ports, respectively. In various embodiments, individual optical ports of any of these four sets may be used for receiving and transmitting light.

[0087] In some embodiments, the optical port of the IOCS device may include a surface optical coupler (e.g., a grating coupler) configured to couple a beam of light incident on the optical port in a direction perpendicular to the main surface of the substrate on which the waveguide is fabricated to the waveguide of the IOCS device. For example, the surface optical coupler may couple light from an optical fiber vertically positioned above the surface optical coupler to the waveguide of the IOCS device. As another example, the surface optical coupler may couple light from another surface optical coupler vertically positioned above the surface optical coupler to the waveguide of the IOCS device. FIG2C schematically illustrates an exemplary IOCS device 202 having an optical port 206 including a surface optical coupler. In some embodiments, the IOCS device 202 may include one or more features described above with respect to the IOCS device 200. In the illustrated example, the first and second plurality of optical ports 106, 108 providing optical connections to the first and second plurality of waveguides 104 include a surface optical coupler 205. In some embodiments, two adjacent (e.g., close-to-close) surface optical couplers may be located at different longitudinal positions relative to the edge of the IOCS device 202, allowing them to receive light from two adjacent waveguides (e.g., two optical fibers). Advantageously, this configuration of the optical surface couplers (shown in Figure 2C) provides more space between the two optical surface couplers for placing optical fibers and prevents optical crosstalk between the surface optical couplers when light is received from two other surface optical couplers vertically positioned above the respective optical surface coupler (e.g., on a second substrate).

[0088] In some embodiments, IOCS devices 200, 201, and 202 may include multiple optical switches formed at multiple crossover regions between the first and second plurality of waveguides 102, 104 to controllably couple individual waveguides in the first plurality of waveguides 102 to individual waveguides in the second plurality of waveguides 104. In some embodiments, the multiple optical switches may be configured to controllably couple an optical port at a first edge of the IOCS device to an optical port at a second edge of the IOCS device. For example, when optical switch 210 of IOCS devices 200, 201, and 202 is in an ON state (Actuated) and all optical switches between optical port A1 and optical switch 210 are in an OFF state, optical switch 210 couples optical port A1 to optical port B3 and reroutes light received by optical port A1 to optical port B3, and vice versa. When all optical switches associated with the waveguide optically connected to optical port A1 are in an OFF state, optical port A1 is decoupled from optical ports B3 to Bm, and light received by optical port A1 is transmitted through the corresponding crossover region.

[0089] In some embodiments, a plurality of optical switches may be configured to controllably couple an optical port at a first edge of the IOCS device to an optical port at a second edge of the IOCS device or an optical port at a third edge of the IOCS device. An example of this IOCS device is shown in Figure 2D. In this example, optical switches 211a and 211b are configured to controllably couple optical port A1 (at the first edge of the IOCS device 203) to optical port B3 (at the second edge of the IOCS device 203) and / or optical port B4 (at the third edge of the IOCS device 203). For example, when optical switch 211a is in the ON state and all optical switches between optical port A1 and optical switch 211a are in the OFF state, optical switch 211a reroutes light received from optical port A1 to optical port B3. As another example, when optical switch 211b is in the ON state and all optical switches between optical port A1 and optical switch 211b are in the OFF state, optical switch 211b reroutes light received from optical port A1 to optical port B4.

[0090] In some embodiments, the switching unit (SC) may include a waveguide cross and two optical switches configured to controllably couple a first waveguide associated with the SC to a second waveguide. In some such embodiments, the first optical switch may be configured to controllably couple a first optical port connected to the first waveguide to a second optical port connected to the second waveguide, and the second optical switch may be configured to controllably couple the first optical port to a third optical port connected to the second waveguide. In some embodiments, the first, second, and third optical ports may be located at three different edges of the IOCS device.

[0091] In various embodiments, individual optical ports among the first, second, third, or fourth plurality of optical ports 106, 108, 112, or 113 can be used bidirectionally as optical inputs (e.g., for receiving light from an optical fiber, device, or optical waveguide on another PIC) and optical outputs (e.g., for transmitting light to an optical fiber, device, or optical waveguide on another PIC).

[0092] In some implementations, by selectively activating some optical switches, a pair of optical connection mappings can be established between a first and a second plurality of optical ports 106 and 112 (e.g., ports “A” and “B”), and the connection configuration can be changed as desired by controlling the state of the optical switches.

[0093] In some embodiments, an optical switch controllably coupled from the first waveguide to the second waveguide can be configured such that when the optical switch is actuated (in the ON state), the amount of optical power passing through the corresponding cross-section of the first waveguide is less than 1%, less than 3%, less than 5%, or less than 10%. In some embodiments, when the first waveguide is optically coupled to the first optical port and the second waveguide is optically coupled to the second optical port, when the optical switch is actuated, more than 90%, more than 95%, more than 97%, or more than 99% of the optical power received from the first optical port can be rerouted by the optical switch to the second optical port (e.g., via a shunt waveguide of the optical switch optically coupled to the first and second waveguides).

[0094] In some embodiments, the bus waveguides of the first or second plurality of bus waveguides may extend from a first end that is optically connected and optically communicates with an optical port to a second end that is optically connected to an optical element. In some embodiments, the optical element may be fabricated on a waveguide layer, substrate, or wafer on which the bus waveguide is fabricated. For example, IOCS device 200 (FIG. 2A) may be part of an IPC fabricated on a wafer, and waveguides 102 and / or 104 may be optically connected to one or more photonic components (e.g., photodetectors, modulators, filters, directional couplers, wavelength multiplexers, and the like).

[0095] In some embodiments, ports on a substrate, chip, or wafer may include optical couplers configured to couple light from external optical waveguides (e.g., optical waveguides not fabricated on the same substrate, chip, or wafer). In some embodiments, ports on a substrate may include fiber couplers configured to optically connect bus waveguides fabricated on the same substrate as the fiber waveguides. In some embodiments, optical ports on a substrate may include vertical optical couplers configured to optically connect bus waveguides fabricated on the same substrate to bus waveguides on another substrate. For example, optical ports B1...Bm may include vertical optical couplers fabricated on wafer 1 and optically connectable to waveguide 104 on wafer 2.

[0096] In some implementations, the IOCS device may include a single die and the corresponding bus waveguide may be optically connected to an external optical waveguide (e.g., optical fiber) via multiple optical ports.

[0097] In some embodiments, an IOCS device (e.g., IOCS device 200, 201, 202, or 203) may include two bonded integrated circuits or may be formed by bonding two integrated circuits. In various embodiments, the integrated circuit may include a photonic integrated circuit (PIC) and / or a microstructure substrate. In some embodiments, the integrated circuit may include an optical waveguide, an optical switch, a MEMS actuator, a microelectromechanical structure, or microstructure features for active or passive alignment of the integrated circuit with another integrated circuit or wafer. In some embodiments, the integrated circuit may be formed on a substrate, a wafer, a die, or the like.

[0098] In some embodiments, portions of the elements of the IOCS device may be fabricated on a first substrate, while the remaining elements are fabricated on a second substrate prior to bonding the two substrates to form the IOCS device. In some embodiments, bonding the two substrates may include aligning the two substrates (passive and / or active) and flip-chip bonding them together. In some embodiments, bonding may include wafer-level bonding. For example, two wafers, each including microstructural features, may be bonded to form a bonded wafer comprising multiple IOCS devices. In some embodiments, portions of the fabrication steps (e.g., releasing a MEMS actuator) may be performed after bonding the two wafers. In some embodiments, the bonded wafer may be divided into multiple individual IOCS devices using a dicing tool.

[0099] In some embodiments, a first plurality of bus optical waveguides or waveguides 102 (associated with port "A") may be formed on a first substrate or wafer "wafer 1", and a second plurality of bus optical waveguides or waveguides 104 (associated with port "B") may be formed on a second substrate or wafer "wafer 2". In some embodiments, the first plurality of waveguides 102 of wafer 1 may be located generally in a first waveguide layer of wafer 1 extending parallel to the main surface of wafer 1, and the second plurality of waveguides 104 of wafer 2 may be located generally in a second waveguide layer of wafer 2 extending parallel to the main surface of wafer 2. In some embodiments, wafer 2 may be located above and bonded to wafer 1 such that the first and second waveguide layers are generally parallel to each other and the two sets of waveguides 102, 104 form a plurality of intersection regions, wherein the intersection regions include areas where protrusions (e.g., vertical protrusions) of waveguides in the second waveguide layer overlap with waveguides in the first waveguide layer (e.g., on wafer 1). It should be understood that the waveguide of wafer 1 is optically isolated and does not physically intersect with the waveguide of wafer 2; however, in a top view, they may appear to intersect within an intersection area. For example, the top view of the IOCS device 201 shown in Figure 2B may be a top view of wafer 1 (which includes a first plurality of bus waveguides 102) aligned with and overlapping wafer 2 (which includes a second plurality of bus waveguides 104). In some embodiments, wafer 1 may include a first plurality of spacer portions and wafer 2 may include a second plurality of spacer portions, wherein, when wafer 1 and wafer 2 are joined, the spacer portions of wafer 1 and the corresponding spacer portions of wafer 2 form spacer structures configured to define a vertical spacing between the first and second waveguide layers. In some embodiments, the spacer or mechanical stop portions may extend vertically away from the corresponding wafer. In various embodiments, the spacer (or mechanical stop) portions may have any cross-sectional shape, including but not limited to circular, rectangular, elliptical, square, triangular, or similar shapes. The first spacer portion formed on wafer 1 and the second spacer portion formed on wafer 2 can contact or join to form a spacer structure defining a vertical gap between the first and second waveguide layers.

[0100] In some embodiments, wafer 1 may include a first plurality of bonding pads or regions, and wafer 2 may include a second plurality of bonding pads or regions. In such embodiments, bonding wafer 1 to wafer 2 may include bonding the first and second plurality of bonding pads or regions. In some embodiments, the first and second plurality of bonding pads may include first and second plurality of spacer portions. Thus, in some embodiments, the first plurality of spacers (or mechanical stops) may be bonded to the second plurality of wafers to provide bonding between wafers 1 and 2 and to establish a vertical spacing between wafers 1 and 2. The spacers disclosed herein may be used, for example, in integration schemes in which at least a portion of an optical switch and / or actuator is released before bonding the wafers (“pre-bonding MEMS release process”). In this integration scheme, because the spacers may be primary mechanical structures that contact and engage with each other, the spacers should have this considerable cross-sectional area or width to provide sufficient mechanical support during and after the bonding process. In some embodiments, the cross-sectional area of ​​the spacer or mechanical stop portion may be greater than 10 square micrometers, greater than 100 square micrometers, greater than 300 square micrometers, greater than 500 square micrometers, or greater than 700 square micrometers, greater than 1000 square micrometers, or any value greater or smaller than these values ​​within any range formed by these values. Although the spacer is described in this paragraph as being present on both wafers 1 and 2, the embodiments are not limited thereto. In some embodiments, the spacer may be provided on one of wafers 1 and 2 but not the other. It should be understood that, in addition to the width or cross-sectional area, the height of the first and second spacers is also strictly controlled so that the optical switch can be effectively switched by mechanical coupling between the waveguides in wafers 1 and 2.

[0101] In some embodiments, a first plurality of waveguides 102 of wafer 1 may be located substantially in a first waveguide layer of wafer 1 parallel to the main surface of wafer 1, and a second plurality of waveguides 104 may be located substantially in a second waveguide layer parallel to the main surface of wafer 2, wherein the second waveguide layer is clamped to wafer 1 via a plurality of anchors formed on wafer 1 such that the first and second plurality of waveguides 102, 104 form a matrix of cross regions described above. In some embodiments, the second waveguide layer may include a support layer and a second plurality of waveguides 104 formed on the support layer but may not include a substrate. The support layer may be substantially thinner than the substrate. For example, the support layer may include buried oxide left after the bulk portion of a silicon-on-insulator (SOI) wafer has been removed. In some embodiments, the anchors among the plurality of anchors may be formed on wafer 1 and extend vertically away from wafer 1. The anchors disclosed herein may be used, for example, in integration schemes where portions of optical switches and / or actuators are released after wafer bonding (“post-bonding MEMS release process”). In this integration scheme, the sacrificial material supporting the optical switch and / or actuator spacer provides mechanical support and additional bonding interfaces. In some embodiments, the anchor may have a smaller cross-sectional area or width relative to the spacer described above in the context of the MEMS release process before bonding. In various embodiments, the anchor may have any cross-sectional shape, including but not limited to circular, rectangular, elliptical, square, triangular, or similar shapes. In some embodiments, the anchor may be less than 100 square micrometers, less than 10 square micrometers, or less than 1.0 square micrometers. Although the anchor is described as being present on wafer 1 in this paragraph, the embodiments are not limited thereto. In some embodiments, the anchor may be provided on both wafers 1 and 2 in a manner similar to that described above with respect to the MEMS release process before bonding. It should be understood that, in addition to the width or cross-sectional area, the height of the anchor is also strictly controlled so that the optical switch can be effectively switched by mechanical coupling between waveguides in wafers 1 and 2.

[0102] According to the various embodiments described herein, wafers 1 and 2 can be directly bonded to each other. In direct bonding, chemical bonds are formed directly between suitable surfaces without the use of adhesives. Advantageously, cryogenic direct bonding can be used to achieve flexibility in integrated materials. When cryogenic direct bonding is employed, the bonding can be performed at temperatures below about 400°C, 300°C, 200°C, and 100°C, or even room temperature, or at temperatures within the range defined by any of these temperatures. The suitable surfaces formed by the spacers or anchors comprise Si, SiO2, and metals. According to some embodiments described herein, wafers 1 and 2 can be mixed and directly bonded to each other. However, the embodiments are not limited thereto, and in other embodiments, adhesives may be used.

[0103] In some embodiments, the shunt waveguides of the optical switches of an IOCS device (e.g., IOCS device 200, 201, 202, or 203) may be formed in an intermediate waveguide layer above a first waveguide layer and below a second waveguide layer. As manufactured, the intermediate waveguide layer may be vertically separated from the first and second waveguide layers. In some embodiments, the vertical spacing between the intermediate waveguide layer and the first and / or second waveguide layers may be from 0.1 μm to 0.5 μm, 0.5 μm to 1 μm, 1 μm to 2 μm, 2 μm to 5 μm, 5 μm to 7 μm, or greater. In some embodiments, the intermediate waveguide layer may be suspended above the first waveguide layer and supported by a clamping structure attached to or on a substrate on which the first waveguide layer is formed. In some embodiments, the intermediate waveguide layer may include shunt waveguides and support structures configured to support the shunt waveguides. In some embodiments, the support structure may include a flexible support structure configured to movably support the end regions of each shunt waveguide such that they can move vertically toward the first or second waveguide layer.

[0104] In some embodiments, the bus optical waveguide and shunt optical waveguide of the IOCS device may comprise polycrystalline silicon, single-crystal silicon, silicon nitride, or other materials. In some embodiments, for light having wavelengths within the operating wavelength range of the IOCS and its switching units, the bus optical waveguide and shunt optical waveguide of the IOCS device may have propagation losses of less than 1 dB / cm, less than 0.5 dB / cm, less than 0.1 dB / cm, less than 0.01 dB / cm, or smaller. In some embodiments, the operating wavelength range of the IOCS or its switching units may be from 400 nm to 1100 nm to 1200 nm, from 1200 nm to 1400 nm, 1400 nm to 1500 nm, from 1500 nm to 1600 nm, from 1260 nm to 1360 nm, from 1450 nm to 1650 nm, or any range greater or smaller than those values.

[0105] Optical switching unit (SC)

[0106] Figure 3A schematically illustrates a top view and two side cross-sectional views of an exemplary switching unit (SC) 208 in the off state. The switching unit 208 may be a switching unit 208 in IOCS devices 200, 201, 202, or 203, as shown in Figures 2A, 2B, 2C, and 2D. SC 208 may include portions of a first waveguide 302 of a first plurality of waveguides 102 and a portion of a second waveguide 304 of a second plurality of waveguides 104 near the intersection region of the first and second waveguides 302, 304. The first waveguide 302 and the second waveguide 304 are vertically separated. SC 208 may further include an optical switch configured to controllably couple the first waveguide 302 to the second waveguide 304. When the optical switch is in the off state, the first and second waveguides 302, 304 are optically decoupled from each other. The optical switch may include a shunt waveguide 306 and one or more MEMS actuators. The shunt waveguide 306 is vertically (and optically) separated from the first and second waveguides 302, 304 and extends longitudinally from a first end above the first waveguide 302 to a second end below the second waveguide 304. In some embodiments, the shunt waveguide 306 can be connected to or anchored to the substrate via a switch anchor configured to suspend the shunt waveguide such that the end region of the shunt waveguide is movable relative to the substrate and the first and second waveguides 302, 304. In the off state, for sufficient optical decoupling, the vertical spacing between the shunt waveguide and the first and / or second waveguides 302, 304 can be a value from 0.1 μm to 0.5 μm, from 0.5 μm to 1 μm, from 1 μm to 2 μm, from 2 μm to 3 μm, from 3 μm to 4 μm, or a value within the range defined by any of these values, or a greater value. In some embodiments, the intermediate portion of the shunt waveguide between the first end region 306a and the second end region 306b can be held in place or fixed by a clamping support structure connected to the first waveguide layer or the substrate on which the first waveguide 302 is formed. In the off state, one or both of the first end region 306a (near the first end of the shunt waveguide 306) and the second end region 306b (near the second end of the shunt waveguide 306) can be vertically (and optically) separated from the corresponding of the first waveguide 302 and the second waveguide 304. In some embodiments, the first end region 306a (also referred to as the first coupling region) can be positioned above the first waveguide 302 such that when an actuator moves the first end region 306a toward the first waveguide 302, the first end region 306a becomes optically coupled to the first waveguide 302. Similarly, the second end region 306b (also known as the second coupling region) may be positioned below the second waveguide 304 such that when the actuator moves the end region 306b toward the second waveguide 304, the second end region 306b becomes optically coupled to the second waveguide 304.In some embodiments, a first MEMS actuator can control the vertical position of a first end region 306a relative to a first waveguide 302, and a second MEMS actuator can control the vertical position of a second end region 306b relative to a second waveguide 304. In some embodiments, the first and second MEMS actuators may include electrostatic actuators. In some other embodiments, the first MEMS actuator may include a capacitive electrostatic actuator, and the second MEMS actuator may include one or more seesaw actuators. In various other embodiments, the first and second MEMS actuators may include (but are not limited to) electrothermal, thermal, magnetic, electromagnetic, electrostatic comb actuation, magnetostrictive, piezoelectric, fluid, pneumatic actuators, and the like. In various embodiments, the MEMS actuator may include a piezoelectric actuator comprising a piezoelectric material configured to operate in different longitudinal, transverse, shear, or other modes. The piezoelectric material may include inorganic or organic piezoelectric materials. Inorganic piezoelectric materials may include single crystals or ceramics (e.g., lithium niobate, quartz, aluminum nitride, PMN-pT, PZN-PT or the like) or polymers (e.g., PVDF, polyimide or the like); however, the embodiments are not limited thereto, and other materials may be used.

[0107] Figure 3B schematically illustrates a close-up view of the second end region 306b of the shunt waveguide 306 and a second MEMS actuator including the first 310a and the second 310b for a seesaw actuator. Figure 3C schematically illustrates a close-up view of the first end region 306a of the shunt waveguide 306 and a flexible support structure movably supporting the first end region 306a. In some embodiments, the end regions 306a and / or 306b of the shunt waveguide 306 may include a tapered region having a width that tapers toward the end of the shunt waveguide 306. In some embodiments, when the coupling region having the tapered region is actuated and bent toward the corresponding bus waveguide, an adiabatic optical coupler may be formed from the end region and the bus waveguide, thereby allowing low-loss adiabatic transfer of optical power from the bus waveguide to the shunt waveguide 306, and vice versa. Thus, tapering the end region of the shunt waveguide reduces optical insertion loss in the optical coupling from the shunt waveguide 306 to the first and second waveguides, and vice versa. In some implementations, SC 208 may include two or more conductive lines or electrodes electrically connected to the first and second MEMS actuators and configured to electrically connect the MEMS actuators to electronic circuitry, the electronic circuitry controlling the state of the optical switch by providing or not providing an actuation signal to the MEMS actuators.

[0108] In some embodiments, activating the optical switch to the ON state includes actuating a first actuator (e.g., a MEMS actuator) to move the first end region 306a toward the first waveguide 302 and actuating a second actuator to move the second end region 306b toward the second waveguide 304. When SC 208 and therefore the optical switch are in the OFF state, the vertical spacing between the shunt waveguide 306 and the first and second waveguides 302, 304 may be sufficiently large to prevent optical coupling between them. In some embodiments, when the optical switch is in the OFF state, a portion of the light coupled from the first waveguide 302 to the second waveguide 304 (or vice versa) may exist but not exceed 3%, 2%, 1%, 0.1%, 0.01%, or less. When SC 208 and thus the optical switch are in the ON state, the first and second end regions 306a and 306b move toward the first and second waveguides 302 and 304, respectively (e.g., the first end region 306a moves upward and the second end region moves downward), so that the first and second end regions 306a and 306b are optically coupled to the first and second waveguides 302 and 304, respectively. Therefore, when the optical switch is in the ON state, light propagating in one of the first or second waveguides 302 and 304 is coupled to the other of the first and second waveguides 302 and 304 via the shunt waveguide 306.

[0109] Figure 4 schematically illustrates a top view and two side cross-sectional views of an exemplary switching unit (SC) 208 when the optical switch and therefore SC 208 are in the ON state. As described above and shown in Figure 4, the first and second end regions 306a and 306b of the shunt waveguide 306 move close to the first and second waveguides 302 and 304, respectively. In some embodiments, the first and second end regions 306a and 306b may not be in contact with the first and second waveguides 302 and 304, respectively. In some embodiments, when SC 208 is in the ON state, the gap size (d) between the first end region 306a (or the second end region 306b) and the first waveguide 302 (or the second waveguide end region 304) may be from λ / 100 to λ / 10, from λ / 10 to λ / 8, from λ / 8 to λ / 6, from λ / 6 to λ / 4, from λ / 4 to λ / 2, where λ is the wavelength of the light rerouted by SC 208. In some embodiments, when the optical switch is in the ON state, the vertical distance between the first and second end regions 306a, 306b and the first and second waveguides 302, 304 may be small enough to cause more than 90%, more than 93%, more than 95%, or more than 97% of the light propagating toward the end region of the shunt waveguide 306 in one of the first or second waveguides 302, 306 to be transmitted via the shunt waveguide 306 to the other of the first and second waveguides 302, 306. In some embodiments, the first and second end regions 306a, 306b may be in contact with the first and second waveguides 302, 304, respectively.

[0110] In some embodiments, when the optical switch is in the ON state, a designated portion of the light propagating toward the end region of the shunt waveguide 306 in one of the first or second waveguides 302, 304 is transmitted via the shunt waveguide 306 to the other of the first and second waveguides 302, 304. In some embodiments, the designated portion may be a value from 1% to 5%, from 5% to 10%, from 10% to 30%, from 30% to 50%, 50% to 70%, from 50% to 70%, from 70% to 90%, from 90% to 95%, from 95% to 99%, or a value within a range defined by any of these values, or a greater value.

[0111] In some implementations, the first and second MEMS actuators and / or the actuation signals provided to the first and second MEMS actuators can be configured to control the strength of the optical coupling between the first and second end regions 306a, 306b of the shunt waveguide 306 and the corresponding waveguide.

[0112] In some embodiments, in the ON state, the vertical distance between the first and second end regions 306a, 306b and the corresponding first and second waveguides 302, 304 may be a value or smaller within the range defined by any of these values, ranging from 0.5 μm to 0.3 μm, from 0.3 μm to 0.2 μm, from 0.2 μm to 0.1 μm, from 0.1 μm to 0.01 μm. In some embodiments, in the OFF state, the vertical distance between the first and second end regions 306a, 306b and the corresponding first and second waveguides 302, 304 may be a value or larger within the range defined by any of these values, ranging from 0.1 μm to 1 μm, 1 μm to 2 μm, 2 μm to 3 μm, 3 μm to 4 μm.

[0113] In various embodiments, the switching unit 208 may be fabricated on a silicon substrate using semiconductor manufacturing methods and processes.

[0114] Figure 5A schematically illustrates a vertical cross-sectional side view of SC 208 along a curved section A'A, showing corresponding portions of the first and second waveguides 302, 304, the shunt waveguide 306, and the MEMS actuators controlling the end regions 306a, 306b of the shunt waveguide 306. In some embodiments, the shunt waveguide 306 may be suspended by a switch anchor 508 extending from the middle region of the shunt waveguide 306 and located between the two end regions 306a, 306b of the shunt waveguide 306 and the substrate (not shown) on which the first waveguide 302 is formed. The switch anchor 508 may be configured to allow movement of the end regions 306a, 306b relative to the substrate and the first and second waveguides 302, 304.

[0115] In the illustrated example, the first MEMS actuator (which controls the first end region 306a) is a capacitive actuator, comprising a first actuation electrode disposed on an intermediate waveguide layer including the shunt waveguide 306 and a second actuation electrode disposed on the first waveguide layer or a substrate on which the first waveguide layer is fabricated. In this particular example, the first MEMS actuator may include two actuation electrodes and, in some embodiments, includes a flexible support structure 308 (shown in FIG. 3C). In some embodiments, the first MEMS actuator can be activated by generating a potential difference between the first and second actuation electrodes and thereby applying an electrostatic force to the first end region 306a of the shunt waveguide 306 to move the first end region 306a toward the first waveguide 302. When the potential difference between the first and second actuation electrodes is removed, the flexible support structure 308 moves the first end region 306a away from the first waveguide 302 back to its neutral position. In some implementations, the coupling gap between the first end region 306a and the first waveguide 302, and the optical coupling strength therethereby, can be tuned or adjusted by tuning or adjusting the potential difference between the first and second actuation electrodes of the first MEMS actuator.

[0116] In the example shown in Figure 5A, the second MEMS actuator controlling the second end region 306b includes two pairs of seesaw actuators. Figure 5B schematically illustrates a top close-up view of an optical switch near the second end region 306b, showing the tapered end of the shunt waveguide 306 mechanically coupled to the two pairs of seesaw actuators. In some embodiments, each seesaw actuator includes a lever beam 504 rotatably connected to a substrate or waveguide layer via a torsion joint 506 and an electrostatic actuator (e.g., a capacitive actuator including two electrodes) configured to rotate the lever beam 504 about a pivot 507 connected to the torsion joint 506. In some embodiments, a first end 501 of the lever beam 504 includes an electrode 503, and a second end of the lever beam 504 is mechanically coupled to the second end region 306b of the shunt waveguide 306. In some embodiments, the second MEMS actuator can be activated by providing a potential difference between electrode 503 and an electrode disposed on the first waveguide layer or substrate, causing a first end 501 of lever beam 504 to move downward toward the first waveguide layer or substrate, thereby causing a second end of lever beam 504 to rise and push the second end region 306b of shunt waveguide 306 toward the second waveguide 304. In some embodiments, upon actuation, electrode 503 is electrostatically attracted to the electrode disposed on the first waveguide layer in a vertical direction generally normal to the main surface of the first waveguide layer, causing the corresponding lever beam 504 to rotate about the corresponding torsion joint 506. When the potential difference between electrode 503 and the corresponding electrode in the first waveguide layer is removed, the second region 306b moves away from the second waveguide 304 back to its neutral position and the first end of lever beam 504 returns to its original position. In some implementations, the coupling gap between the second end region 306b and the second waveguide 304, and the optical coupling strength therethereby, can be tuned or adjusted by tuning or adjusting the potential difference between the electrode 503 and the corresponding electrode on the first waveguide layer.

[0117] As configured, when the optical switch is in the off state, no MEMS actuator is actuated and the shunt waveguide 306 is in a neutral position with sufficient vertical spacing from the first and second waveguides 302, 304, and the light propagating in these waveguides is unaffected by the shunt waveguide 306. When the optical switch is in the on state, both the first and second MEMS actuators (e.g., two pairs of seesaw actuators) are actuated to move the first end region 306a downward and the second end region 306b upward, such that the light propagating in one of the first and second waveguides 302, 304 is optically coupled into the shunt waveguide 306 and then optically coupled into the other of the first and second waveguides 302, 304.

[0118] Integrated optical circuit switch

[0119] As described above, integrated optical circuit switching (IOCS) device configurations (e.g., IOCS devices 200, 201, 202, 203) can be implemented in different process integration schemes or architectures.

[0120] It should be understood that some process integration schemes or architectures of IOCS devices may share certain common features and characteristics described below with respect to an instance IOCS device.

[0121] In some embodiments, the IOCS device may include a first substrate (e.g., a first wafer or chip), a first waveguide layer formed on the first substrate, an intermediate waveguide layer suspended above the first waveguide layer and mechanically connected to the first substrate via a first plurality of anchors, and a second waveguide layer suspended above the intermediate waveguide layer. Referring back to Figures 2A to 2D, the first waveguide layer may include a first plurality of waveguides 102, the second waveguide layer may include a second plurality of waveguides 104, and the intermediate waveguide layer may include a plurality of shunt waveguides configured to optically couple individual of the first and second plurality of waveguides 102, 104 at respective intersection regions. The first substrate may also include MEMS actuators configured to control the shunt waveguides. In some embodiments, a portion of each MEMS actuator (e.g., one or more electrodes) may be included in the intermediate waveguide layer. For example, a MEMS actuator (e.g., one of the MEMS actuators of SC 208) may include a first electrode formed on the first substrate and a second electrode formed on the second waveguide layer in a region above the first electrode. In some embodiments, the first and second waveguide layers may include buffer layers on which one or more waveguides are formed. In some embodiments, the waveguides may include silicon or silicon nitride and the buffer layers may include silicon dioxide or another material having a lower refractive index than silicon or silicon nitride. In some embodiments, the waveguides and buffer layers may include other materials, provided that the buffer layer has a lower refractive index than the waveguides.

[0122] In various embodiments, the substrate may include a bulk layer having a thickness from 100 micrometers to 2000 micrometers or greater. In some embodiments, the substrate may include a top buffer layer having a refractive index lower than that of the bulk portion of the substrate. For example, the substrate may include a bulk portion comprising silicon and a top layer comprising silicon dioxide. In some embodiments, multiple waveguides may be formed in the buffer layer using photolithography and etching (referred to herein as photolithographic patterning). For example, silicon waveguides may be formed on the silicon dioxide buffer layer. In some embodiments, the substrate may include a bulk substrate without any buffer layer.

[0123] In various embodiments, the waveguide layer may include a layer formed on a substrate. In some embodiments, the waveguide layer may include a buffer layer, an optical waveguide formed on the buffer layer, and in some embodiments, additional structures such as portions of spacer structures, alignment structures, electrical interconnects, portions of MEMS actuators, and the like. In some such cases, the buffer layer that mechanically supports the optical waveguide and other structures fabricated thereon may be referred to as a support layer. In various embodiments, the thickness of the waveguide layer may be less than 10 micrometers, less than 30 micrometers, less than 50 micrometers, less than 70 micrometers, or less than 100 micrometers.

[0124] In some embodiments, an IOCS device may include one or more waveguides optically coupled to the IOCS and configured to couple light from an external waveguide (e.g., an optical fiber) or the device to one or more waveguides of the IOCS device and to one or more optical ports thereof. In various embodiments, the optical ports may be disposed on or formed on a first waveguide layer, a second waveguide layer, or both.

[0125] In some embodiments, the IOCS device may include an interlayer optical coupler configured to vertically couple an optical port or waveguide on a first waveguide layer to an optical port or waveguide on a second waveguide layer. In some embodiments, the interlayer optical coupler may include a first portion formed on the first waveguide layer and a second portion formed on the second waveguide layer, wherein the first portion is optically coupled to the second portion. In some other embodiments, the interlayer optical coupler may include a first portion formed on the first waveguide layer, a second portion formed on an intermediate waveguide layer, and a third portion formed on a third waveguide layer, wherein the first portion is optically coupled to the second portion, and the second portion is optically coupled to the third portion. In some other embodiments, portions of the interlayer optical coupler may be surface-mount optical couplers, grating couplers, tapered waveguides, or multiple vertically stacked and optically coupled waveguides.

[0126] In some embodiments, an IOCS device may include alignment structures configured to facilitate or achieve active or passive alignment of two wafers during its fabrication, the two wafers being bonded to form the IOCS device. In some embodiments, a first wafer may include a first plurality of alignment structures and a second wafer may include a second plurality of alignment structures associated with the first plurality of alignment structures. In some embodiments, alignment structures may be formed on first and second waveguide layers. In some embodiments, alignment structures may be formed on portions of the wafer outside the region where the IOCS device is formed (e.g., around the IOCS device and closer to the edge of each wafer). In some embodiments, a first alignment structure of the first plurality of alignment structures may be paired with a second alignment structure of the second plurality of alignment structures. In various embodiments, alignment structures may include optical waveguide portions, a pair of waveguide portions, one or a pair of surface optical couplers, reference marks, protrusions, openings, grooves, and the like. In various embodiments, alignment structures may include passive optical alignment structures, active optical alignment structures (collectively referred to as optical alignment structures), and self-aligning structures (referred to as physical alignment structures). In some embodiments, a first active alignment structure (e.g., on a first wafer) may include a pair of optically isolated waveguide portions, and a second active alignment structure (e.g., on a second waveguide layer) may include a waveguide structure configured to optically couple to the first active alignment structure when the two wafers are aligned. In some embodiments, a first passive individual alignment structure (e.g., on a first waveguide layer) may include a first alignment mark, and a second passive alignment structure (e.g., on a second waveguide layer) may include a second alignment mark configured to match or pair with the first passive alignment structure when the two wafers are aligned.

[0127] In some embodiments, individual self-alignment structures may include protrusions, pins, openings, holes, V-grooves, and the like. In some embodiments, a first self-alignment structure (e.g., on a first wafer) may include a pin or protrusion, and a second self-alignment structure (e.g., on a second wafer) may include an opening or hole (e.g., a V-groove) configured to receive a pin such that when the pin mechanically engages with an opening, the two wafers become aligned. Further details regarding the application of alignment structures and exemplary alignment structures are described below.

[0128] Figures 6A and 6B schematically illustrate first (Figure 6A) and second (Figure 6B) side cross-sectional views of an exemplary IOCS device 600 according to a first process architecture embodiment. The second cross-sectional side view is rotated 90 degrees relative to the first cross-sectional side view (around an axis perpendicular to the main surface of the first substrate 602). The IOCS device 600 may include a first waveguide layer formed on the first substrate 602, an intermediate waveguide layer located above the first waveguide layer and mechanically connected to the first substrate via at least a first plurality of anchors, and a second waveguide layer located above the intermediate waveguide layer. Figures 6A and 6B show a first individual waveguide 302 of a first plurality of waveguides 102 (Figures 2A to 2D), a second individual waveguide 304 of a second plurality of waveguides 104 (Figures 2A to 2D), a shunt waveguide 306 of a plurality of shunt waveguides, a support layer 604 on which a second plurality of waveguides are formed, two anchors 605 of a first plurality of anchors, a switch anchor 508 of a plurality of switch anchors, and a lever beam (not shown) of a plurality of lever beams also associated with an actuator. In the integration scheme shown in Figure 6A, the first substrate 602 may include a top buffer sublayer (not shown) on which the first waveguide 304 is formed.

[0129] As further detailed elsewhere in this specification, the IOCS device 600 can be manufactured using an integrated approach, wherein portions of the optical switch and / or actuator are released after the wafer is bonded (“Post-Bond MEMS Release Process”). In this approach, the first and second waveguides 302, 304 are first fabricated separately on their respective substrates. The optical switch, including the shunt waveguide 306, is fabricated on a first substrate 602 on which the first waveguide 302 has been formed. Components of the optical switch may be embedded in a sacrificial material, such as an oxide selectively etched relative to the material of the optical switch prior to bonding a second substrate (not shown) on which the second waveguide 304 is formed. In some instances, an anchor 605 may be formed on the first substrate 602 and embedded in the sacrificial material. The second waveguide 304 may optionally also have its own sacrificial material formed thereon. After bonding the two substrates, the optical switch and / or actuator can be released by removing the sacrificial material. Subsequently, the bulk substrate on which the second waveguide 304 is located can be removed, thereby leaving a support layer 604, which may be, for example, a buried oxide layer of an SOI wafer. As described above, in this integration scheme, in the context of the MEMS release process prior to bonding, the anchor can have a smaller cross-sectional area or width relative to the cross-sectional area or width of the aforementioned spacers because the sacrificial material supporting the optical switches and / or actuator spacers and the additional bonding pads provides sufficient mechanical support.

[0130] In some embodiments, the IOCS device 600 may include alignment structures used during the manufacturing process (e.g., for aligning the first substrate 602 and the second substrate). In some embodiments, the alignment structures formed on the substrate or wafer used to manufacture the first embodiment (e.g., the IOCS device 600) may not include self-aligning structures.

[0131] In this first embodiment, the second waveguide layer of the IOCS device 600 includes a support layer 604 that can be suspended by and mechanically connected to a first substrate 602 via a second plurality of anchors 605 (both shown). In such embodiments, the thickness and weight of the second waveguide layer, including the support layer 604 and the second plurality of waveguides, can be configured such that it can be stably suspended and supported by the second plurality of anchors. For example, the thickness of the second waveguide layer or the support layer 604 may be less than an upper limit and / or the second waveguide layer may not be connected to the substrate or may be disposed on the substrate. In some embodiments, the upper limit thickness of the second waveguide layer may be from 0.1 micrometers to 1 micrometer, from 1 micrometer to 2 micrometers, from 2 micrometers to 10 micrometers, from 10 micrometers to 20 micrometers, from 20 micrometers to 30 micrometers, from 30 micrometers to 50 micrometers, from 50 micrometers to 100 micrometers, or from 200 micrometers to 800 micrometers. In some embodiments, the thickness of the second waveguide layer may be less than 800 micrometers. In some embodiments, the thickness of the second waveguide layer may be less than 10 micrometers. In some embodiments, the second waveguide layer may consist of a support layer, a plurality of waveguides, an alignment structure, and an interlayer optical coupler formed on the support layer. In some embodiments, the anchors of the second plurality of anchors may be attached to the first substrate and extend vertically away from the first substrate. In various embodiments, the anchors may have any cross-sectional shape, including but not limited to circular, rectangular, elliptical, square, triangular, or similar shapes. In some embodiments, the cross-sectional area of ​​the anchors may be less than 100 square micrometers, less than 10 square micrometers, or less than 1.0 square micrometer.

[0132] The first IOCS embodiment described above with respect to Figures 6A to 6B can be manufactured using a first manufacturing method. Referring to Figure 6C, according to an embodiment, the first manufacturing method for manufacturing the IOCS device 600 may include the following manufacturing steps:

[0133] Method 650 includes: a first fabrication step, including fabricating a first waveguide layer 652 and an optical switch structure on a first substrate 602. In some embodiments, the first waveguide layer may be formed or disposed on the first substrate 602 and the optical switch structure may be formed or disposed on the first waveguide layer. In some embodiments, the optical switch structure may include layers, regions, electrodes, and / or structures that can be used to form an optical switch at a waveguide crossover region during the performance of one or more additional processes. In some embodiments, the optical switch structure may be formed at least partially by forming an intermediate waveguide layer over the first waveguide layer. In some embodiments, as fabricated, the optical switch structure may include a micromechanical structure (also referred to as a microelectromechanical system (MEMS) structure) and a shunt waveguide fixed by a sacrificial material (e.g., an oxide selectively etched relative to the materials of the MEMS actuator and the optical switch). The MEMS structure may include layers and regions associated with a MEMS actuator. In some embodiments, the MEMS structure may include a MEMS actuator embedded in a sacrificial layer, the sacrificial layer being selectively etched such that the MEMS actuator can be released by etching the sacrificial layer. Therefore, additional processes are required to fabricate the optical switch (e.g., forming a MEMS actuator, suspending a shunt waveguide, removing the sacrificial layer, or other processes). These additional processes can be performed in subsequent fabrication steps after the first substrate is bonded to the second substrate. In some embodiments, the optical switch structure may include a shunt waveguide at least partially embedded in the sacrificial material. In some embodiments, the first waveguide layer may include at least a first plurality of bus optical waveguides 102 extending along a first direction from a first edge of the first substrate to a second edge of the first substrate. In some embodiments, the first waveguide layer may further include portions of the optical switch, portions of an interlayer optical coupler, portions of an alignment structure, electrodes, optical ports, portions of anchors (e.g., shunt waveguide anchors and / or second-layer anchors), and / or one or more of a bonding region or bonding pad. In some embodiments, the first substrate may additionally include portions of a mechanical stop.

[0134] In some embodiments, at least some regions, areas, or volumes within the first wafer may include a sacrificial layer or material. In some embodiments, the sacrificial layer or material may be configured to temporarily support components of an optical switch. The sacrificial layer may also provide a surface thereon to which a second waveguide layer is bonded. Anchors 605 may be formed before or after the deposition of the sacrificial material. In some embodiments, anchors 605 may be formed after the deposition of the sacrificial layer and may include a vertical path through the second waveguide layer and further through the sacrificial material. Anchors 605 (e.g., vertical paths) may act as mechanical supports for the second waveguide layer (e.g., support layer 604 and second bus optical waveguide 304) and maintain vertical spacing (e.g., predefined vertical spacing) between the first and second plurality of waveguides. Additionally, in some embodiments, anchors 605 may provide an electrical connection between the first and second waveguide layers. For example, the anchor of anchor 605 may include a conductive wire connecting a first electrical or optoelectronic component (e.g., an electrical device, photodetector, conductive pad, or conductive live wire) disposed on or within the first waveguide layer to a second electrical or optoelectronic component disposed on or within the second waveguide layer. In some implementations, vertical pathways formed by material selectively etched relative to the sacrificial material are removed from the gap between the first and second waveguide layers during the manufacturing process.

[0135] In some implementations, the sacrificial layer may comprise an oxide or organic or inorganic material that can be selectively removed without affecting the structural properties of surrounding structures such as bus waveguides, shunt waveguides, MEMS actuators, alignment structures, interlayer couplers, optical ports, and the like.

[0136] Referring again to FIG. 6C, method 650 further includes: in a second manufacturing step, fabricating a second waveguide layer 654 on a second substrate (removed in FIG. 6A and 6B). In some embodiments, the second waveguide layer may include a second plurality of bus optical waveguides extending in a second direction from a first edge of the second substrate to a second edge of the second substrate opposite to the first edge. In some embodiments, the second direction may be substantially perpendicular to the first direction along which the first plurality of waveguides extend. In some embodiments, the second substrate may further include electrodes, optical ports, portions of interlayer optical couplers, portions of alignment structures, portions of mechanical stops, and / or bonding areas or bonding pads. In some embodiments, fabrication 654 of the second substrate may further include portions of electrodes, optical ports, portions of interlayer optical couplers, portions of alignment structures, portions of anchors (e.g., shunt waveguide anchors and / or second waveguide layer anchors), and / or bonding areas or bonding pads.

[0137] In some embodiments, the second waveguide layer may include a support layer 604, which may be, for example, a buried oxide layer of an SOI wafer. In some embodiments, a second plurality of bus optical waveguides are formed on the support layer 604.

[0138] As mentioned above, the first and second substrates may include alignment structures for alignment prior to bonding. In some embodiments, the alignment structures may include passive alignment structures, such as patterns (e.g., etched or raised patterns) or markings (also referred to as reference marks) on the two substrates (or dies). In some embodiments, the alignment structures may include active alignment structures configured for active optical alignment of the two substrates. In some embodiments, the active alignment structure may include a loopback waveguide structure comprising waveguide segments on a first substrate and waveguide segments on a second substrate coupled by a grating interlayer coupler or a tapered waveguide interlayer coupler. In some embodiments, the two waveguide segments of an active alignment structure formed on the same substrate may be optically coupled to two optical ports on the substrate to allow measurement optical transmission to be transitioned via the loopback waveguide structure. Exemplary embodiments of active alignment structures are shown in Figures 12A-12B and are described in more detail elsewhere in this application. In some embodiments, the alignment structure may include a self-aligning structure. A self-aligned structure may include a first portion (e.g., an opening or concave portion) on one substrate (e.g., a first substrate) and a second portion (e.g., a pin or convex portion) on another substrate (e.g., a second substrate), wherein the first portion is configured to mechanically couple to the second portion by, for example, receiving the first portion and causing the two substrates to align. Several embodiments of the self-aligned structure are illustrated in Figures 13A to 13H, Figures 14A to 14G, and 15A to 15C, and are described in more detail below.

[0139] In some embodiments, fabricating the first and second substrates may include providing a first (or second) substrate and forming the aforementioned layers, features, and components on the first and second substrates using common microfabrication methods (including, but not limited to, methods for fabricating MEMS actuators and optical structures (e.g., waveguides, vertical couplers, tapered waveguides, and the like), semiconductor fabrication methods, and the like). In some embodiments, the microfabrication methods may include photolithographic mask or photoresist patterning, dry and wet etching, dielectric deposition, metal deposition, electroplating, and the like. In some embodiments, the first and / or second substrates may include bulk substrates (e.g., silicon substrates) or multilayer substrates (e.g., silicon substrates with a top silicon-on-oxide (SOI) layer or silicon substrates with a top oxide layer).

[0140] Referring again to FIG. 6C, method 650 further includes, in a third manufacturing step, aligning 656 the first and second substrates for bonding (e.g., flip-chip bonding). Aligning 656 the first and second substrates may include aligning an optical switch formed on the first substrate to a bus optical waveguide in a second plurality of bus optical waveguides formed on the second substrate. In some embodiments, the first and second substrates in alignment 656 may be aligned to form a waveguide crossover, and a shunt waveguide is properly aligned relative to a corresponding waveguide in the second plurality of waveguides. In some embodiments, properly aligning the shunt waveguide relative to an individual waveguide in the second plurality of waveguides may include positioning and aligning a second end region (second coupling region) of the shunt waveguide below the individual waveguide such that, once manufacturing is complete (e.g., MEMS actuator release), actuating the corresponding optical switch optically couples the shunt waveguide to the individual waveguide based on a predetermined coupling strength. In some embodiments, the predetermined coupling strength may correspond to low-loss optical coupling between waveguides associated with the crossover region (e.g., insertion loss less than 0.1 dB, less than 1 dB, less than 2 dB, or less than 3 dB).

[0141] In some methods of the embodiments, alignment 656 may include passive alignment using a passive alignment structure, active alignment using an active alignment structure, self alignment using a self alignment structure, or a combination thereof.

[0142] An exemplary alignment method compatible with the first manufacturing method includes one or more of the following alignment steps:

[0143] 1) Use passive alignment marks to passively align the first and second substrates. For example, two matching marks located on one of the substrates can be aligned under a microscope by moving (e.g., translating and / or rotating) one substrate relative to the other.

[0144] 2) Active alignment of the first and second substrates to passive alignment is achieved by providing light to a first portion of an active alignment structure on one of the substrates via an optical port (e.g., from an external optical fiber via a fiber coupler) and measuring the light looping back via a second portion of an active alignment structure on the other substrate. In some embodiments, an external laser or emitting diode may be used to provide light and a photodetector may be used to measure and monitor the power of the output light. In some embodiments, the photodetector may be an external photodetector. In some embodiments, the output light may be coupled to and measured by a photodetector integrated on the first or second substrate. One substrate may then be moved (e.g., translated and / or rotated) relative to the other substrate while monitoring the optical output power until a threshold is reached. In some embodiments, the optical power through two or more active alignment structures may be monitored simultaneously and / or sequentially. In some embodiments, two or more active alignment structures may be positioned at different corners of the two substrates. In some embodiments, two sets of active alignment structures may be located at two corners of the two substrates for rotational alignment. In some embodiments, two active alignment structures may be configured for alignment along two generally perpendicular directions parallel to the main surfaces of the first and / or second substrates. In some embodiments, active alignment including a grating interlayer coupler (e.g., a grating coupler) may be used for coarse alignment. In some embodiments, active alignment structures including a tapered waveguide interlayer coupler may be used for fine alignment. Therefore, the alignment process may include coarse alignment steps and fine alignment steps. In some embodiments, the tapered waveguide interlayer coupler may include at least two tapered waveguide portions, each fabricated on one of the first and second substrates and having a tapered end. When the tapered end of one tapered waveguide portion is aligned with the tapered end of another tapered waveguide portion, light may be coupled from one tapered waveguide portion to the other.

[0145] In some embodiments, the alignment process may begin with a self-alignment procedure, wherein three or more self-aligned structures on the first and second substrates are partially aligned and then joined to align the two substrates prior to passive alignment. In some embodiments, the self-alignment step may be performed after passive alignment and before active alignment. In some embodiments, the alignment process may skip the first or second alignment step, change the order of these steps, or include additional steps.

[0146] In some embodiments, the alignment structure is configured such that performing any of the above alignment processes results in at least partial alignment (e.g., simultaneous alignment) of interlayer optical couplers on two substrates and / or alignment of shunt waveguides with corresponding waveguides of a second plurality of waveguides.

[0147] Referring again to FIG. 6C, method 650 further includes a fourth manufacturing step, comprising bonding 658 of a first substrate aligned with a second substrate to a second substrate using any suitable flip-chip bonding or wafer bonding method. The first and second substrates may be bonded face-to-face, wherein one or both of the substrates may have a sacrificial material formed on one side that can contact the opposing surfaces during bonding. In some embodiments, bonding may occur between bonding areas and pads provided on the two substrates, and the two substrates may be suitable for direct bonding as described above. In some embodiments, bonding 658 may include bonding the first substrate 602 to the second substrate by bonding the front surface of the second wafer to the front surface of the first wafer, wherein the front surface of the first wafer includes sacrificial material. In some embodiments, the vertical spacing between the first and second substrates and thereby between the first and second bus optical waveguides is established by a sacrificial layer formed on the first substrate.

[0148] Referring again to Figure 6C, method 650 further includes a fifth manufacturing step, which includes removing 660 the second substrate from the second waveguide layer. Removing 660 the second substrate may include back-side grinding, dry etching, and / or wet etching to thin the second substrate to a suitable thickness. In one example, when the second substrate is an SOI wafer on which the second waveguide layer is formed, the bulk portion of the SOI wafer may be removed by grinding and wet etching, stopping at the buried oxide.

[0149] Referring again to FIG. 6C, method 650 further includes a sixth manufacturing step, which includes processing 662 the layer between the first and second substrates (e.g., between the first and second waveguide layers) to release a MEMS actuator, form an optical switch, release a shunt waveguide, form anchors supporting the shunt waveguide, and / or form a plurality of anchors holding and / or supporting the second waveguide layer above the first waveguide layer. In some embodiments, forming a plurality of anchors holding and / or supporting the second waveguide layer may include forming a plurality of vertical pathways through the second waveguide layer and further through sacrificial material. These vertical pathways may act as mechanical anchors to secure the second waveguide layer (e.g., support layer 604 and a second bus optical waveguide formed thereon) to the first substrate 602 or the first wafer and maintain a vertical spacing (e.g., a predefined vertical spacing) between the first and second plurality of waveguides. In some embodiments, the anchors supporting the second waveguide layer may provide electrical connectivity between the first and second waveguide layers. In some embodiments, the anchors supporting the second waveguide layer may include conductive pathways. In some implementations, the anchor supporting the second waveguide layer may include a conductive path, and may include a dielectric region. In some such instances, the anchor may include a conductive line extending from the first waveguide layer to the second waveguide layer via the dielectric region.

[0150] In some embodiments, processing these layers may further include a suspended shunt waveguide and / or a suspended second waveguide layer. The resulting optical switch may include a suspended shunt waveguide and a MEMS actuator configured such that, upon actuation, it optically couples the first and second end regions of the suspended shunt waveguide to a bus optical waveguide (e.g., bus optical waveguide 302) of a first plurality of bus optical waveguides and a waveguide (e.g., bus optical waveguide 304) of a second plurality of bus optical waveguides, respectively.

[0151] Figures 7A and 7B schematically illustrate first (7A) and second (7B) side cross-sectional views of an exemplary IOCS device 700 according to a second process architecture embodiment. The second cross-sectional side view is rotated 90 degrees relative to the first cross-sectional side view (around an axis perpendicular to the main surface of the first substrate 602). The IOCS device 700 may include a first waveguide layer formed on the first substrate 602, an intermediate waveguide layer located above the first waveguide layer and mechanically connected to the first substrate at least via a first plurality of anchors, and a second waveguide layer located above the intermediate waveguide layer and formed on a second substrate 704. Figures 7A and 7B show a first separate waveguide 302 of a first plurality of waveguides 102 (Figures 2A to 2D), a second separate waveguide 304 of a second plurality of waveguides 104, a shunt waveguide 306 of a plurality of shunt waveguides, a second substrate 704 on which the second plurality of waveguides are formed, a switch anchor 508 of a plurality of switch anchors, and a mechanical stop including mechanical stop portions 702a and 702b. In the integration scheme shown in FIG7A, the first substrate 602 may include a top buffer sublayer (not shown) on which the first waveguide 302 is formed, and the second substrate 704 may include a top buffer sublayer (not shown) on which the second waveguide 304 is formed.

[0152] As further detailed elsewhere in this application, the IOCS device 700 can be manufactured using an integrated approach, in which at least a portion of the optical switch and / or actuator is released before bonding the wafer (“pre-bonding MEMS release process”). In this approach, the first and second waveguides 102, 104 are first fabricated separately on their respective substrates 602, 704. The optical switch, including the shunt waveguide 306, is fabricated on the first substrate 602 on which the first waveguide 302 has been formed. In a manner similar to the integrated approach described above with respect to Figures 6A and 6B, the components of the optical switch can be first buried in a sacrificial material (e.g., an oxide selectively etched with respect to the optical switch). The second waveguide 304 can also be formed using a sacrificial material. However, unlike the integrated approach described with respect to Figures 6A and 6B, the sacrificial material is removed from both substrates 602, 704 before bonding the first and second substrates 602, 704. That is, the optical switch and / or actuator can be released by removing the sacrificial material before bonding the two substrates. As described above, in this integration scheme, because sacrificial material is removed from both substrates, the mechanical stop portions 702a and 702b can be primary mechanical structures that are in contact with and engaged with each other. Therefore, the spacers can have a considerable cross-sectional area or width to provide sufficient mechanical support during and after the bonding process.

[0153] In some embodiments, the IOCS device 700 may include alignment structures used during the manufacturing process (e.g., for aligning the first substrate 602 and the second substrate 704). In some embodiments, the alignment structures formed on the substrate or wafer used to manufacture the first embodiment may include passive alignment structures, active alignment structures, self-aligned structures, or combinations thereof.

[0154] In this second embodiment, the second waveguide layer of the IOCS device 700 is suspended and supported by a second substrate 704, which is bonded to the first substrate 602 via first and second plurality of bonding regions or bonding pads formed on the first and second substrates 602 and 704, respectively, and may also be bonded at other locations. In some embodiments, the second waveguide layer may be formed on the second substrate 704. In some embodiments, the thickness of the second substrate may be greater than 100 micrometers, greater than 500 micrometers, greater than 700 micrometers, greater than 1000 micrometers, or greater. In some embodiments, the IOCS device 700 may include a plurality of mechanical stops (also referred to as spacers) 702 configured to define or establish vertical spacing between the first and second substrates 602 and 704 and thereby between the first and second plurality of waveguides. In some embodiments, each mechanical stop may include a first stop portion 702a connected to the first substrate 602 and a second mechanical stop portion 702b connected to the second substrate 704. In some embodiments, the ends of the first and second stop portions 702a, 702b opposite to the respective substrates may be mechanically contacted or engaged. In some embodiments, a plurality of mechanical stops may be formed by contacting a first plurality of stop portions 702a formed on a first substrate 602 with a second plurality of stop portions 702b formed on a second substrate 704. In various embodiments, the stop portions may have any cross-sectional shape, including but not limited to circular, rectangular, elliptical, square, triangular, or similar shapes. In some embodiments, the cross-sectional area of ​​the mechanical stops may be greater than 10 square micrometers, or greater than 100 square micrometers, greater than 500 square micrometers, or within any range of these values, or greater or less. In some embodiments, a first plurality of engagement regions or pads may include the first plurality of stop portions and a second plurality of engagement regions or pads may include the second plurality of stop portions.

[0155] In some embodiments, the IOCS device 700 may include one or more conductive lines connecting a first electrical or optoelectronic component (e.g., an electrical device, photodetector, conductive pad, or conductive live wire) disposed on or within a first waveguide layer or on a first substrate 602 to a second electrical or optoelectronic component disposed on or within a second waveguide layer or on a second substrate 704. In some embodiments, the conductive lines may be formed from first and second stop portions 702a, 702b.

[0156] The second IOCS embodiment described above with respect to Figures 7A to 7B can be manufactured using the second manufacturing method. Referring to Figure 7C, according to an embodiment, the second manufacturing method 750 for manufacturing the IOCS device 700 may include the following manufacturing steps:

[0157] The second manufacturing method 750 includes: in a first manufacturing step, fabricating a first waveguide layer 754 and an optical switch structure on a first substrate 602. In some embodiments, the first waveguide layer is formed or disposed on the first substrate 602 and the optical switch structure may be formed or disposed on the first waveguide layer. In some embodiments, the optical switch structure may include one or more features described above with respect to the first manufacturing method.

[0158] In some embodiments, the first waveguide layer may include at least a first plurality of bus optical waveguides 102 extending along a first direction from a first edge of the first wafer to a second edge of the first wafer. In some such cases, the first waveguide layer may further include one or more of the following: portions of an optical switch, portions of an anchor, portions of an interlayer optical coupler, portions of an alignment structure, and bonding regions or bonding pads. In some embodiments, the first substrate may further include portions of electrodes, optical ports, interlayer optical couplers, anchors (e.g., shunt waveguide anchors), portions of alignment structures, and / or bonding regions or bonding pads. In some embodiments, the first wafer may include portions of mechanical stops.

[0159] Referring again to FIG. 7C, method 750 further includes: a second manufacturing step comprising processing 756 a layer and structure formed on a first substrate to release a MEMS actuator and form an optical switch. In some embodiments, the processing layer may further include a suspended shunt waveguide. The resulting optical switch may include a suspended shunt waveguide 306 and a MEMS actuator configured such that, upon actuation, it optically couples a first end region of the suspended shunt waveguide 306 to a bus optical waveguide (e.g., bus optical waveguide 302) among a first plurality of bus optical waveguides and optically couples a second end region of the suspended shunt waveguide to a second bus optical waveguide (e.g., bus optical waveguide 304) above the optical switch.

[0160] Referring again to FIG. 7C, method 750 further includes: in a third manufacturing step, fabricating 758 a second waveguide layer on the second substrate 704. In some embodiments, the second waveguide layer may include a second plurality of bus optical waveguides extending in a second direction from a first edge of the second substrate to a second edge of the second substrate opposite to the first edge. In some embodiments, the second direction may be substantially perpendicular to the first direction along which the first plurality of waveguides extend. In some embodiments, the second substrate may further include electrodes, optical ports, portions of interlayer optical couplers, portions of alignment structures, portions of mechanical stops, and / or bonding areas or bonding pads.

[0161] In some embodiments and as part of method 750, the second waveguide layer may include a buffer layer and a second plurality of bus optical waveguides formed on the buffer layer. The second plurality of bus optical waveguides may extend from a first edge of the second substrate to a second edge of the second substrate along a second direction. In some embodiments, the second direction may be substantially perpendicular to the first direction along which the first plurality of waveguides extend. In some embodiments, the second waveguide layer may further include optical ports, portions of interlayer optical couplers, portions of alignment structures, and / or bonding regions or bonding pads. In some embodiments, the alignment structure may include the features and structures described above with respect to the first manufacturing method. Similarly, the first and third manufacturing steps (manufacturing 754 and manufacturing 758) may include one or more features described above with respect to the first and second manufacturing steps of the manufacturing method described above with respect to FIG. 6C.

[0162] Referring again to FIG. 7C, method 750 further includes a fourth manufacturing step, which includes aligning the first and second substrates 760 for bonding (e.g., flip-chip bonding). Alignment 760 may include aligning an optical switch formed on the first substrate with a second waveguide formed on the second substrate. In some embodiments, the first and second substrates may be aligned to form a waveguide crossover, and the shunt waveguide is properly aligned relative to a corresponding waveguide in a second plurality of waveguides. In some embodiments, properly aligning the shunt waveguide relative to an individual waveguide in the second plurality of waveguides may include positioning and aligning a second end region (second coupling region) of the shunt waveguide below the individual waveguide such that actuating the corresponding optical switch optically couples the shunt waveguide to the individual waveguide based on a predetermined coupling strength. In some embodiments, the predetermined coupling strength may correspond to low-loss optical coupling between waveguides associated with the crossover region (e.g., insertion loss less than 0.1 dB, less than 1 dB, less than 2 dB, or less than 3 dB).

[0163] In some embodiments, based on the exemplary alignment method described above with respect to FIG. 6C, the alignment process may include passive alignment, active alignment, self-alignment, or a combination thereof. In some embodiments, the alignment process may begin with a self-alignment procedure, wherein three or more self-aligned structures on the first and second substrates are partially aligned and then joined to align the two substrates prior to passive alignment. In some embodiments, the self-alignment step may be performed after passive alignment and before active alignment. In some embodiments, the alignment process may skip the first or second alignment step described above, change the order of these steps, or include additional steps.

[0164] In some embodiments, the alignment structure is configured such that performing any of the above alignment processes results in at least partial alignment (e.g., simultaneous alignment) of interlayer optical couplers on two substrates and / or alignment of shunt waveguides with a second or more waveguides.

[0165] In some embodiments, the alignment structure is configured such that performing any of the above alignment processes results in at least partial alignment (e.g., simultaneous alignment) of interlayer optical couplers on the two substrates, alignment of shunt waveguides with corresponding waveguides in a second plurality of waveguides, partial alignment of junction areas (or pads) on the two substrates, and / or partial alignment of mechanical stops on the two substrates.

[0166] Referring again to FIG. 7C, method 750 further includes, in a fifth manufacturing step, bonding 762 of a first substrate 602 aligned with the second substrate 704 to the second substrate 704 using a common flip-chip bonding method. In some embodiments, bonding may occur between bonding regions and pads provided on the two substrates. In some embodiments, bonding 762 may include bonding the first substrate 602 to the second substrate 704 by bonding the front surface of the second wafer to the front surface of the first wafer.

[0167] In some embodiments, mechanical stops can establish a predefined vertical spacing between the first and second waveguide layers and thereby establish vertical spacing between the second and a second plurality of waveguides. For example, a first stop portion 702a connected to the first substrate 602 can mechanically contact a second stop portion 702b connected to the second substrate 704 to form a mechanical stop 702 extending from the top surface of the first substrate 602 (or the first waveguide layer) to the top surface of the second substrate 704 (or the second waveguide layer). The height of the resulting mechanical stop (which may be substantially equal to the vertical spacing between the two waveguide layers (e.g., a predefined vertical spacing)) can be from 0.5 micrometers to 1 micrometer, from 1 micrometer to 3 micrometers, from 3 micrometers to 7 micrometers, from 7 micrometers to 10 micrometers, or greater. In some embodiments, the bonding region and / or pad may include stop portions on both substrates. In some such cases, the ends of the first and second stop portions 702a, 702b opposite to the respective substrates can be bonded during the bonding process.

[0168] As described above, the first and second IOCS embodiments described above with respect to Figures 6A to 6B and 7A to 7B can be manufactured using at least two different manufacturing methods that include the “pre-bonding MEMS release process” and the “post-bonding MEMS release process” described herein. The two different manufacturing methods may include a first step of manufacturing a first wafer (wafer 1) or die, a second step of manufacturing a second wafer (wafer 2) or die separated from the first wafer or die, a third step of aligning the first and second wafers or dies, and a fourth step of bonding the two wafers or dies. The first manufacturing method differs from the second manufacturing method in that the first manufacturing method includes at least two additional steps after the fourth step (e.g., the fifth and sixth manufacturing steps described herein), and the first manufacturing step of the first manufacturing method may omit certain processes performed after the fourth manufacturing step (e.g., during the sixth manufacturing step described herein) (e.g., the MEMS actuator release process described herein).

[0169] In some embodiments, bus optical waveguides (referred to herein as waveguides), optical ports (e.g., fiber-to-chip couplers), interlayer optical couplers (e.g., tapered waveguides or grating couplers), MEMS actuators or MEMS structures, mechanical stops, electrodes and electrical connections, and other structures are first fabricated individually on the first and / or second wafers. In some embodiments, a first plurality of waveguides, shunt waveguides, and MEMS actuators may be fabricated on the first wafer, and a second plurality of waveguides may be fabricated on the second wafer. In some embodiments, after one or more of these structures and components are completed or partially fabricated, the two wafers may be aligned and bonded (e.g., flip-chip bonding). In one embodiment, the two fabricated wafers are bonded using a wafer-level bonding method. In another embodiment, the two fabricated wafers are first diced into chips (or dies), and the chips from the first wafer and the corresponding chips from the second wafer are bonded, for example, through a precision assembly process. In some embodiments, the vertical spacing between the first and second wafers may be partially maintained by mechanical stops fabricated on one or both wafers.

[0170] In some embodiments, the alignment methods and processes described above are generally used to align two wafers or two substrates, each comprising a portion of an integrated photonic circuit. In some embodiments, the processes described above can be used to fabricate optical devices and / or optical device portions on different substrates or wafers or on two or more substrates or wafers. In some embodiments, these optical devices and / or optical device portions may not have any movable areas. In some embodiments, these optical devices and / or optical device portions may not contain MEMS actuators. In some embodiments, the processes described above can be used to evanescently couple optical devices and / or optical device portions fabricated on different substrates or wafers or on two or more substrates or wafers.

[0171] In various embodiments, fabricating the first and second waveguide layers (e.g., fabrication 652, 654, 754, and 758 of fabrication methods 650 and 750) may include photolithographic patterning to form an optical bus waveguide extending within the waveguide layer on the front side of the substrate. In some embodiments, patterning may include depositing a mask layer over the unstructured waveguide layer, photolithographically patterning the mask, and etching (e.g., dry or wet etching) exposed portions of the unstructured waveguide layer to form a waveguide layer including optical structures (e.g., bus optical waveguides, optical alignment structures) or other structures.

[0172] In some embodiments, fabricating the first and second waveguide layers may further include forming alignment structures, electrical contacts, portions of MEMS actuators, portions of optical switches, bonding regions, portions of mechanical spacers, or portions of anchors (e.g., anchors supporting shunt waveguides or the second waveguide layer). In some embodiments, the alignment structure may include waveguide structures and / or segments, such as portions of optical isolation pairs of optical waveguides (e.g., generally parallel optical waveguides), interlayer couplers (e.g., grating couplers, tapered waveguide couplers, or the like), and loopback waveguide structures (e.g., U-shaped waveguide segments).

[0173] Optical port arrangement

[0174] As described above with respect to Figures 2A to 2D, IOCS devices such as IOCS devices 200, 201, 202, and 203 may include two waveguide layers and multiple optical ports configured to optically couple bus optical waveguides to external optical components, such as fiber optic waveguides. In various embodiments, all optical ports may be formed (or disposed) on one of the two waveguide layers of the IOCS device or may be distributed between the two waveguide layers. For example, referring back to Figures 2A to 2D, a first plurality of optical ports 106 (optical port group “A”) and a third plurality of optical ports 112 (optical port group “B”) may be located on the same wafer or on different wafers. In some embodiments, for example when all optical ports are located on one of the waveguide layers, a bus optical waveguide formed on the other waveguide layer may be optically coupled to some of the optical ports via an interlayer coupler (e.g., a grating or tapered waveguide coupler). In some embodiments, the tapered waveguide interlayer optical coupler may include one or more stages of thermally insulating waveguide couplers formed between the ends of two tapered waveguides. As an example, this tapered waveguide interlayer optical coupler is shown in Figures 11A to 11C and described below.

[0175] In some embodiments, the optical port may include a fiber-to-waveguide coupler (also known as a fiber-to-chip or fiber coupler) for coupling light between one or more external optical fibers to the bus optical waveguide of the IOCS device. In various embodiments, the fiber coupler may include surface optical couplers (e.g., grating couplers), edge couplers, evanescent couplers, microlens couplers, and other types of suitable optical couplers.

[0176] Figures 8A to 8D schematically illustrate top views (8A to 8B) of the first and second substrates (or wafers) 602 and 704 used to fabricate an exemplary IOCS device (such as the IOCS device 200 shown in Figure 2A) and side views (8C to 8D) of the resulting IOCS device. In this example, all optical ports 206 are located on the second substrate 704, and the first plurality of waveguides 102 are optically coupled to corresponding optical ports on the second substrate 704 via a plurality of interlayer optical couplers 802. The plurality of interlayer optical couplers 802 may include a first plurality of interlayer coupler portions 802a formed or disposed on the first substrate 602 and a second plurality of interlayer coupler portions 802b formed or disposed on the second substrate 704. In the example shown, the first group of interlayer couplers 802 is placed between the first plurality of optical ports (“A1”, “A2”...“Am”) 106 on the second substrate 704 and the first ends of the corresponding bus optical waveguides of the first plurality of bus optical waveguides 102 on the first substrate 602, and the second group of interlayer couplers 802 is placed between the second plurality of optical ports (“C1”, “C2”...“Cm”) 108 on the second substrate 704 and the second ends of the corresponding first plurality of bus optical waveguides 102 on the first substrate 602.

[0177] Figures 9A to 9D schematically illustrate top views (9A to 9B) of the first and second substrates (or wafers) 602, 704 used to fabricate an exemplary IOCS device (e.g., IOCS device 201 shown in Figure 2B) and side views (9C to 9D) of the resulting IOCS device. In this example, all optical ports 206 are located on the first substrate 602, and a second plurality of waveguides 104 are optically coupled to corresponding optical ports on the first substrate 602 via a plurality of interlayer optical couplers 802. The plurality of optical couplers 802 may include a first plurality of interlayer coupler portions 802a formed or disposed on the first substrate 602 and a second plurality of interlayer coupler portions 802b formed or disposed on the second substrate 704. In the illustrated example, a first group of interlayer couplers 802 is positioned between a third plurality of optical ports (“B1”, “B2”...“Bm”) 112 on the first substrate 602 and a first end of a corresponding bus optical waveguide on the second substrate 704. In the illustrated example, the second ends of the first and second plurality of waveguides 102, 104 may be optically connected to optical devices and components formed or disposed on one or both of the first and second substrates.

[0178] Figures 10A to 10D schematically illustrate top views (10A to 10B) of the first and second substrates (or wafers) 602 and 704 used to fabricate an exemplary IOCS device (e.g., IOCS device 200 shown in Figure 2A) and side views (10C to 10D) of the resulting IOCS device. In this example, a first plurality of optical ports 106 are located on the first substrate 602 and a third plurality of optical ports 112 are located on the second substrate 704. Therefore, this IOCS device does not include any interlayer optical couplers configured to optically couple waveguides to the optical ports. The first plurality of waveguides 102 are directly connected to the first plurality of optical ports 106 and the second plurality of waveguides 104 are directly connected to the third plurality of optical ports 112.

[0179] In the examples shown in Figures 8C to 8D, 9C to 9D and 10C to 10D, shunt waveguide 806 is actuated to couple a bus optical waveguide formed on a first substrate 602 to a bus optical waveguide on a second substrate 704, while other shunt waveguides 804 are in a neutral position that is optically decoupled from the bus optical waveguides of the first and second substrates 602 and 704.

[0180] In some embodiments, the pitch of the plurality of optical ports 206, and in some implementations, the pitch of the corresponding waveguides, may be selected to be substantially equal to the pitch of the fiber array coupled to the plurality of optical ports. In some embodiments, the pitch of the plurality of waveguides may be smaller than the pitch of the fiber array. The density of the waveguides and the corresponding optical switch matrix may be greater than the density of the fiber array.

[0181] Interlayer coupler

[0182] In various embodiments, an IOCS device (e.g., IOCS device 200, 201, 202, or 203) may include one or more interlayer optical couplers configured to optically connect a waveguide or waveguide segment on a first waveguide layer to a second waveguide layer vertically separated from the first waveguide layer. In some embodiments, the interlayer optical coupler may be optically connected to a waveguide segment forming an active alignment structure. In some embodiments, the interlayer waveguide coupler may be optically connected to an individual waveguide on one of the waveguide layers of the IOCS device and optically connected to an optical port located on another waveguide layer of the IOCS device. In other instances, the interlayer waveguide coupler may be optically connected to an individual waveguide on one of the waveguide layers of the IOCS device to optically connect the individual waveguide to another waveguide or optical device located on another waveguide layer of the IOCS device.

[0183] In some embodiments, an interlayer optical coupler (also referred to as an interlayer coupler) may include a first portion on a first substrate or waveguide layer and a second portion on a second substrate or waveguide layer, wherein the first and second portions are optically coupled via free space or guided light propagation or evanescent coupling. In some embodiments, the two portions of the interlayer coupler may be substantially similar or different.

[0184] In some embodiments, each part of the interlayer coupler (e.g., a grating interlayer coupler) may include a surface coupler (e.g., a grating coupler) configured to convert light received from the waveguide on the waveguide layer into light (e.g., a beam of light) propagating away from the waveguide in a vertical direction perpendicular to the main surface of the waveguide layer and to couple light normally incident on the waveguide layer (e.g., a beam of light emitted from another surface coupler) to the waveguide.

[0185] In some embodiments, each portion of an interlayer coupler (e.g., a tapered waveguide interlayer coupler) may include a coupler waveguide segment having a first end optically connected to a bus optical waveguide or waveguide segment of an active alignment structure and a second end (coupling end) configured to gradually couple to another coupler waveguide segment vertically positioned above the coupler waveguide segment. In some embodiments, the coupling end of the coupler waveguide segment may include a tapered end having a width that tapers from a first width (e.g., the width of the bus optical waveguide) to a second width smaller than the first width. In some embodiments, the second width may be 50%, 25%, 10%, or less of the first width. Advantageously, when the two coupling ends gradually couple, the resulting coupling junction (thermally adiabatic coupling junction) can transmit light from one waveguide coupler segment to another. Figures 11A to 11C schematically illustrate an exemplary tapered waveguide interlayer coupler including a top view (Figure 11A), a side view (Figure 11B), and a perspective view (Figure 11C) of a first coupler waveguide segment 802a and a second coupler waveguide segment 802b, both having tapered coupling ends. In some embodiments, waveguide segments 802a and 802b may be substantially parallel to each other. In some embodiments, the first coupler waveguide segment 802a is formed on a first waveguide layer and the second coupler waveguide segment 802b is formed on a second waveguide layer vertically separated from the first waveguide layer. The first coupler waveguide segment 802a may be aligned relative to the second coupler waveguide segment 802b such that one tapered end is above the other tapered end and the two tapered ends overlap longitudinally and laterally. In some embodiments, a percentage greater than 20%, 50%, or 90%, or any of these values, of the tapered portions may overlap longitudinally. In some embodiments, the vertical spacing between the first and second coupler waveguide segments 802a, 802b can be from 10% to 200% of the wavelength of the light coupled by the tapered waveguide interlayer coupler. In some embodiments, the optical insertion loss between the two evanescently coupled waveguide segments 802a, 802b can be very sensitive to the lateral (y-axis) and longitudinal (x-axis) alignment between the first and second coupler waveguide segments 802a, 802b. Therefore, the tapered waveguide interlayer coupler can be used for fine alignment between the first and second substrates during the fabrication process of the IOCS device. In some embodiments, compared to the tapered waveguide interlayer coupler, the insertion loss of the grating interlayer coupler can be less sensitive to the lateral and longitudinal alignment between two vertically separated grating portions. Therefore, the grating interlayer coupler can be used for coarse alignment between the first and second substrates during the fabrication process of the IOCS. In some implementations, the optical insertion loss between the two evanescently coupled waveguide segments 802a and 802b is less sensitive to the longitudinal alignment between the first and second coupler waveguide segments 802a and 802b than to the lateral alignment between the first and second coupler waveguide segments 802a and 802b.Therefore, lateral alignment with the tapered waveguide interlayer coupler can be more precise than longitudinal alignment. In some embodiments, the two substrates (or wafers) of the IOCS device may include portions of a tapered waveguide interlayer coupler oriented in two vertical directions to allow for precise two-dimensional alignment.

[0186] Active alignment structure

[0187] As described above, during the manufacturing process of an IOCS device, two wafers or chips can be aligned so that, after the IOCS device is bonded and formed, optical switches and interlayer couplers can couple light between waveguides on different waveguide layers or between waveguides on different layers and ports with low insertion loss. One or two wafers can also be divided into separate segments or portions or cut and then aligned and bonded.

[0188] In some embodiments, the two wafers or chips may include active alignment structures configured to maximize the transmission of optical power via the active alignment structures, resulting in an optical coupler with low optical insertion loss via a shunt waveguide and interlayer coupler. In some embodiments, a pair of active alignment structures may be used to actively align two wafers or substrates.

[0189] In some embodiments, the active alignment structure may include a loopback waveguide structure having waveguide segments on two wafers coupled by interlayer couplers (e.g., grating couplers and tapered waveguides). In some embodiments, an optical port (e.g., a fiber coupler) on one of the substrates or wafers may be used to input light into the loopback waveguide structure and couple output light to an external detector. When light is input into the loopback structure and optical power is transmitted via the loopback waveguide structure, active optical alignment between the two wafers or substrates can be performed by substantially maximizing the monitored optical power. In some embodiments, the loopback waveguide structure including the grating interlayer coupler may be used for coarse alignment, and the loopback waveguide structure including tapered waveguide interlayer couplers in two directions (e.g., two vertical directions, such as the x and y directions) may be used for fine alignment. In some embodiments, at least two sets of active alignment structures may be located at at least two corners of each of the substrates for rotational alignment.

[0190] In some embodiments, the first active alignment structure may be formed from a first substrate and the second active alignment structure may be formed from a second substrate. In some embodiments, the first active alignment structure may include two optical isolation elements (e.g., two waveguide portions or two surface couplers). Light may be provided from a light source (e.g., a laser or LED) to a first element of the first active alignment structure, and light output from the second element may be measured using a photodetector, while the second active optical alignment structure moves over the first active alignment structure (e.g., by moving the second substrate over the first substrate). When aligned to the first active alignment structure, the second active alignment structure may receive light from an element of the first active alignment structure and transmit the received light to a second element of the first active alignment structure. Thus, when the first and second active alignment elements are aligned (e.g., lateral and longitudinal alignment), the optical power received from the second element of the first active alignment element may exceed a threshold, such as reaching or approaching a maximum level.

[0191] In some embodiments, the self-aligned structure may be formed on a region of the main surface of a substrate that is different from the region on which layers and / or structures associated with waveguides, optical switches, interlayer couplers, and optical ports are fabricated.

[0192] Figures 12A to 12C illustrate examples of active alignment structures. Figure 12A schematically illustrates a top view of a first substrate or wafer including a first optical switching region 1200a in which elements of an IOCS device are fabricated and a first surrounding region in which a first portion of an active alignment structure is fabricated. In some embodiments, the first surrounding region and the first optical switching region 1200b do not overlap. Figure 12A schematically illustrates a top view of a second substrate or wafer including a second optical switching region 1200b in which elements of an IOCS device are fabricated and a second surrounding region in which a second portion of an active alignment structure is fabricated. In some embodiments, the second surrounding region and the second optical switching region 1200b do not overlap. Figure 12C schematically illustrates a perspective top view of an IOCS device formed by overlapping the first and second substrates when active alignment structures on two wafers are aligned to increase or maximize optical power transmitted via one or more pairs of active alignment structures.

[0193] In the illustrated example, two sets of active alignment structures are located at two corners of each of the first and second substrates 602 and 704 to align the first and second substrates 602 and 704 in a rotational and translational manner. Each set of active alignment structures can optically communicate with external optical sources and detectors via a set of optical ports 1207 (e.g., fiber-to-waveguide optical couplers). In this example, each set of active alignment structures includes a first loop waveguide structure 1202a / b for coarse alignment and second and third loop waveguide structures 1204a / b and 1206a / b for fine alignment in the longitudinal (e.g., along the x-axis) and lateral (e.g., along the y-axis) directions. In addition, each set of active alignment structures includes a single waveguide loop 1208 for optically characterizing waveguides, waveguide segments, and optical ports. The first loopback waveguide structure 1202a / b includes a first element 1202a comprising a pair of grating couplers connected via waveguide segments and a second element 1202b comprising a pair of optically isolating waveguides, each extending from an optical port to the grating coupler. The second loopback waveguide structure 1204a / b includes a first element 1204a comprising a pair of tapered waveguide couplers extending in the x-direction and connected via waveguide segments and a second element 1204b comprising a pair of optically isolating waveguides, each extending in the x-direction from an optical port to the tapered waveguide coupler. The second loopback waveguide structure 1206a / b includes a first element 1206a comprising a pair of tapered waveguide couplers extending in the y-direction and connected via waveguide segments and a second element 1206b comprising a pair of optically isolating waveguides, each extending in the y-direction from an optical port to the tapered waveguide coupler.

[0194] As mentioned above, in some embodiments, active alignment may include a first step of coarse alignment using a grating interlayer coupler loop waveguide (first loop waveguide structure 1202a / b) and a second step of fine alignment using a tapered waveguide interlayer coupler loop waveguide (second and third loop waveguide structures 1204a / b and 1206a / b).

[0195] Self-aligned structure

[0196] In some embodiments, the first and second substrates of the IOCS device may include self-aligned structures configured to facilitate alignment between the substrates during the fabrication of the IOCS.

[0197] In some embodiments, the self-alignment structure may include portions on two substrates configured to mechanically engage and align with each other on the two substrates during engagement. The self-alignment structure may have a convex-concave relationship. In some embodiments, a first alignment structure on a first substrate may include a convex component (e.g., a plurality of pins, protrusions, pillars, segments, tabs, or other forms of protrusions) and a second alignment structure on a second substrate may include a concave component (e.g., a plurality of holes, openings, grooves, notches, passages, trenches, slots, or other forms of recesses) configured to receive a corresponding convex component. In some embodiments, the shape and size of a pair of self-alignment structures on the two substrates may be configured to couple and / or engage within predetermined tolerances suitable for optical coupling of the various components described herein. For example, the concave component may have an opening width that is larger than the convex component by an amount corresponding to the tolerance specifications of the various optical coupling structures described above.

[0198] In some embodiments, both the first and second alignment structures may include concave components or grooves that can be coupled by a third alignment structure that can be inserted into both the first and second alignment structures. For example, the first alignment structure on a first substrate may include a first plurality of grooves and the second alignment structure on a second substrate may include a second plurality of grooves, wherein the first and second grooves are configured to be mechanically coupled to each other by a plurality of microbeads.

[0199] In some embodiments, the self-aligned structure may be formed on a region of the main surface of a substrate that is different from the region on which layers and / or structures associated with waveguides, optical switches, interlayer couplers, and optical ports are fabricated.

[0200] It should be understood that protrusions and grooves of different shapes can be mixed and matched to form parts of a mating alignment structure. Figures 13A to 13C schematically illustrate perspective views of three pairs of substrates (or wafers) having self-aligned structures including protrusions and grooves of different shapes. In the example shown in Figure 13A, the first substrate 602 includes grooves such as elongated V-shaped grooves 1304a / b, and the second substrate 704 includes circular protrusions configured to be received and engaged with, for example, hemispherical protrusions 1302, of the elongated V-shaped grooves. In the example shown in Figure 13B, the first substrate 602 includes four pyramidal openings 1306, and the second substrate 704 includes four hemispherical protrusions 1302 configured to be received and engaged with three pyramidal openings. In the example shown in Figure 13C, the first substrate 602 includes three elongated V-shaped grooves 1304a / b, and the second substrate 704 includes three rectangular protrusions 1308 configured to be received and engaged with the three elongated V-shaped grooves. In some embodiments, a first group of V-grooves may extend along a first direction and a second group of V-grooves may extend along a second direction. The first direction may be substantially perpendicular to the second direction. This relative orientation of the V-grooves facilitates alignment of structures (e.g., shunt waveguides relative to a second plurality of bus optical waveguides) in two dimensions (e.g., along the x-axis and y-axis). In the example shown in Figures 13A to 13C, a first elongated V-groove 1304a formed on a first substrate 602 extends along the first direction and second and third V-grooves 1304b extend along a second direction substantially perpendicular to the first direction.

[0201] Figures 13D to 13F schematically illustrate perspective top views of the three pairs of substrates shown in Figures 13A to 13C, respectively, when the two substrates of each pair overlap and the self-aligned structures on the first and second substrates 602 and 704 partially engage to cause the two substrates to become at least partially aligned.

[0202] Figure 13G schematically illustrates a side-view myopic cross-sectional view of the first or third pair of substrates (shown in Figures 13A and 13C) near the alignment structure when the two substrates of each pair overlap and the self-alignment structures on the first and second substrates 602, 704 are partially joined. Figure 13H schematically illustrates a side-view myopic cross-sectional view of the second pair of substrates (shown in Figure 13B) near the alignment structure when the two substrates of each pair overlap and the self-alignment structures on the first and second substrates 602, 704 are partially joined.

[0203] As illustrated in Figures 13G and 13H, mating alignment structures with the different shapes shown (e.g., hemispherical and V-shaped grooves) can be used to maintain the gap between the bonding substrates. In some embodiments, the first or second substrate may further include one or more spacers or stops 1310 configured to maintain a predetermined vertical distance between the first and second substrates 602, 704.

[0204] Figures 14A to 14C schematically illustrate perspective views of three pairs of substrates (or wafers) having first and second self-aligned structures, each including openings (or holes) of different shapes, wherein an opening on the first substrate 602 is configured to be mechanically coupled to an opening on the second substrate 704 via a third self-aligned structure (e.g., microbeads 1402 (e.g., spherical microbeads)). In the example shown in Figure 14A, the first substrate 602 includes three elongated V-shaped grooves 1304a / b and the second substrate 704 includes three pyramidal openings 1306. In the example shown in Figure 14B, each of the first and second substrates 602, 704 includes three pyramidal openings 1306. In the example shown in Figure 14C, each of the first and second substrates 602, 704 includes four pyramidal openings 1306.

[0205] Figures 14D to 14F schematically illustrate perspective top views of three pairs of substrates shown in Figures 14A to 14C, respectively, when the two substrates of each pair overlap and portions of the self-aligned structures on the first and second substrates 602, 704 are mechanically coupled by three microbeads 1402 to cause the two substrates to become at least partially aligned.

[0206] Figure 14G schematically illustrates a side-view myopic cross-section of three pairs of substrates (shown in Figures 14A to 14C) near the alignment structure when the two substrates of each pair overlap and portions of the self-aligned structure on the first and second substrates 602, 704 are mechanically coupled by microbeads 1402.

[0207] Figure 15A schematically illustrates a perspective view of a pair of substrates (or wafers) having a self-aligned structure including cylindrical protrusions and holes. In the example shown in Figure 15A, the first substrate 602 includes four cylindrical holes 1504 and the second substrate 704 includes four cylindrical protrusions 1502 configured to be received and inserted into the four cylindrical holes 1504.

[0208] Figure 15B schematically illustrates a perspective top view of the substrate pair shown in Figure 15A when the two substrates overlap and the self-aligned structures on the first and second substrates 602, 704 are joined to cause the two substrates to become at least partially aligned.

[0209] Figure 15C schematically illustrates a side-view near-cross-section of the substrate pair shown in Figure 15A near a pair of alignment structures on the first and second substrates 602, 704 when the two substrates overlap and the alignment structures are engaged (cylindrical pins are inserted into cylindrical holes).

[0210] Figure 16A schematically illustrates a perspective view of a pair of substrates (or wafers) having a self-aligned structure including rectangular pillars or protrusions (or protrusions) 1602 and matching rectangular holes (or openings) 1604. In the example shown in Figure 16A, the first substrate 602 includes four rectangular holes 1604 and the second substrate 704 includes four rectangular pillars or protrusions 1602 configured to be received and inserted into the four rectangular holes 1604.

[0211] Figure 16B schematically illustrates a perspective top view of the substrate pair shown in Figure 16A when the two substrates overlap and the matching pairs of the self-aligned structures on the first and second substrates 602, 704 engage to cause the two substrates to become at least partially aligned.

[0212] Figure 16C schematically illustrates a side-view myopic cross-sectional view of the pair of substrates shown in Figure 16A near a pair of alignment structures on the first and second substrates 602 and 704 when the two substrates overlap and the alignment structures are engaged (cubic protrusions are inserted into cubic holes).

[0213] In some embodiments, the self-aligned structures described above relative to Figures 13A to 13F, 14A to 14F, 15A to 15C, 16A to 16C may be formed on two regions of the main surface of each substrate around or on the opposite side of region 1300 of the fabricated layers and / or waveguides, optical switches and interlayer couplers, optical ports and related structures (e.g., anchors).

[0214] In various embodiments, pins (or protrusions) 1302, 1502, 1602 and openings (or holes) 1304a / b, 1504, 1604 may be formed on the substrate using photolithography and / or etching. For example, a polymer or photoresist layer may be disposed on the top layer of the substrate and the protrusions may be fabricated by photolithographic patterning, etching (e.g., wet or dry etching), or a combination thereof, or other known methods.

[0215] In some embodiments, pins (or protrusions) 1302, 1502, 1602 may be directly deposited on the substrate or attached to the substrate as a preformed structure.

[0216] In various embodiments, the pins (or protrusions) 1302, 1308, 1502 and the microbeads may include photoresist, polymer, metal, glass, ceramic, silicon or other materials.

[0217] In some embodiments, the width of the V-groove 1304a / b can be from 100 micrometers to 1000 micrometers and the depth of the V-groove 1304a / b can be from 5 micrometers to 500 micrometers.

[0218] In some implementations, the width of the pyramidal opening can be from 100 micrometers to 1000 micrometers and the depth of the pyramidal opening can be from 5 micrometers to 500 micrometers.

[0219] In some embodiments, the diameter of the cylindrical hole 1504 can be from 10 micrometers to 1000 micrometers and the depth of the cylindrical hole 1504 can be from 5 micrometers to 500 micrometers.

[0220] In some embodiments, the diameter of the spherical microspheres 1402 can be from 10 micrometers to 1000 micrometers and the diameter of the hemispherical protrusions 1302 can be from 10 micrometers to 1000 micrometers.

[0221] In some embodiments, the active alignment structures and / or self-alignment structures described above with respect to Figures 12A-12C and Figures 13A-13F, 14A-14F, 15A-15C, 16A-16C are generally used to align two wafers or two substrates, each comprising a portion of an integrated photonic circuit. In some embodiments, the active alignment structures and / or self-alignment structures are used for optical devices and / or portions of optical devices fabricated on different substrates or wafers of a pair of substrates or wafers. In some embodiments, these optical devices and / or portions of optical devices may not have any movable areas. In some embodiments, these optical devices and / or portions of optical devices may not include MEMS actuators. In some embodiments, the active alignment structures and / or self-alignment structures are used for optical devices and / or portions of optical devices fabricated on different substrates or wafers in a pair of substrates or wafers, evanescently coupled.

[0222] In various embodiments, the actuator in the optical switch of the IOCS device described above may include a piezoelectric MEMS actuator.

[0223] Integrated optical circuit switch with sensor

[0224] In some embodiments, an IOCS (such as the IOCS device described above or any of different types of IOCS) may include one or more monitoring sensors configured to generate sensor signals that can be used to determine the on / off state of an optical switch in the IOCS and / or the amount of light rerouted by the optical switch. In some embodiments, the monitoring sensor may be configured to detect mechanical displacement of a shunt waveguide of the optical switch. In some instances, the monitoring sensor may be an electrical or electromechanical sensor (e.g., a capacitive sensor with a moving plate) for detecting displacement at one or both ends of the shunt waveguide and generating a sensor signal indicating the magnitude of the displacement. In some instances, the monitoring sensor may be a photodetector configured to receive light from an optical waveguide (e.g., a bus optical waveguide or recovery optical waveguide of the IOCS) that receives light via an optical switch. In various embodiments, the monitoring sensor may be a silicon-based, germanium-based photodetector, or a photodetector based on a group III-V semiconductor material. In some embodiments, the monitoring sensor may be a pin photodiode based on any of the above materials (e.g., a germanium pin photodiode). In some instances, the intrinsic region of a pin photodiode used to measure or monitor optical power propagating in a bus optical waveguide may include a portion of the bus optical waveguide. In some such instances, one or more sensor signals (e.g., photocurrent) generated by one or more photodetectors may indicate the amount of light rerouted to the optical waveguide by an optical switch and may be used to determine whether the corresponding optical switch is on or off and / or to determine the efficiency of the optical switch used for rerouting optical power (e.g., the ratio between the optical power received by the optical switch and the optical power rerouted to another bus optical waveguide).

[0225] In various embodiments, the monitoring sensor may be integrated with the IOCS on a common substrate. In some embodiments, at least a portion of the monitoring sensor may include portions of an optical switch or optical waveguide. In some embodiments, at least a portion of the monitoring sensor may be bonded to the IOCS (e.g., a substrate or waveguide layer bonded to the IOCS). In some embodiments, at least a portion of the monitoring sensor may be fabricated on or above the common substrate along with the optical switch or bus optical waveguide.

[0226] In some embodiments, a monitoring sensor may be electrically linked to electronic circuitry (e.g., electronic control and / or processing circuitry) configured to receive sensor signals and determine the on / off state or efficiency of an optical switch based at least in part on the sensor signals. In some cases, the state of the optical switch determined based on one or more sensor signals may be referred to as the measured state of the optical switch. In some embodiments, the electronic circuitry may further receive signals associated with an activation signal provided to the optical switch to determine the expected state of the optical switch and then compare the expected state of the optical switch with the measured state of the optical switch to determine the functionality of the optical switch. For example, when the electronic circuitry detects a difference between the expected and measured states of the optical switch, it may determine that the optical switch has malfunctioned. In some embodiments, the electronic circuitry may use one or more sensor signals to determine the efficiency of the optical switch, compare the determined efficiency with a threshold (e.g., minimum expected efficiency), and generate a signal indicating a faulty or defective optical switch when the determined efficiency is less than the expected value. In some embodiments, when the electronic circuitry determines that the optical switch has malfunctioned (or is defective), the electronic circuitry may generate a warning signal indicating the location (e.g., relative to columns and rows of the optical switch matrix) of the faulty and / or defective optical switch that caused the error. In some embodiments, warning signals may be provided to the user and / or used to resolve errors, such as by modifying (e.g., adding) the activation signal provided to the identified defective (or faulty) optical switch, or by rerouting the optical signal to another bus optical waveguide to avoid the optical path controlled by the defective switch. In some cases, such warning signals may be used to detect defective switches and determine the pass / fail assessment of the IOCS and, in some cases, the wafer including the IOCS, when the IOCS is tested in the factory. In some embodiments, warning signals may be provided to the user via a user interface that communicates with the electronic circuitry. In various embodiments, the electronic circuitry may be connected to the optical switch and / or monitoring sensors via wired or wireless links. In some cases, the electronic circuitry may be integrated with the IOCS on a common chip, mounted on a common carrier chip, or otherwise positioned in the same housing or package as the IOCS. In some embodiments, the electronic circuitry and the IOCS may form an optical system for rerouting optical signals (the optical system being able to monitor the performance of the optical switch on the IOCS) and, in some embodiments, restore the functionality of the IOCS in the event of optical switch failure or malfunction.

[0227] Figure 17A schematically illustrates a top view of an IOCS including a monitoring photodetector (mPD) configured to receive portions of light propagating in first and second plurality of bus optical waveguides 102, 104 formed above the substrate (e.g., in the same or different waveguide layers). In some embodiments, the first and second plurality of bus optical waveguides may be terminated by first and second plurality of optical ports 106, 112 formed above the substrate (e.g., in the same or different waveguide layers). In the illustrated example, some mPDs are directly coupled to the output facet of the bus optical waveguides, and some mPDs are coupled to the bus optical waveguides via optical tap couplers (also referred to as tap couplers). In some cases, the tap coupler may include evanescent coupling to the optical waveguide to reroute portions of the light propagating in the optical waveguide to waveguide segments of the mPD. The mPD may generate a sensor signal indicating the power of the light received via the tap coupler and thereby indicating the total power of the light propagating in the optical waveguide. In various implementations, the portion of light coupled from the waveguide by the tap coupler can be from 0.1% to 1%, from 1% to 3%, from 3% to 5%, from 5% to 8%, from 8% to 10%, or any range greater or less than these values.

[0228] Referring again to Figure 17A, the IOCS device 1701 includes a first plurality of mPDs 1704a configured to receive portions of light propagating in the first plurality of bus optical waveguides 102 (e.g., toward the first plurality of optical ports 106) via optical coupling (e.g., evanescent coupling) to the first plurality of tap couplers of the first plurality of bus optical waveguides 102. In some instances, the first plurality of tap couplers may be located at the first plurality of optical ports 106 (“A1”...“A1”). m The optical switch is optically coupled to a first plurality of bus optical waveguides 102 at a position between the optical switch and the corresponding optical switch, the optical switch being configured to reroute light between the first plurality of bus optical waveguides 102 and the corresponding one of the second plurality of bus optical waveguides 104.

[0229] The IOCS device 1701 may further include a second plurality of mPDs 1704b configured to receive portions of light propagating in the second plurality of bus optical waveguides 104 (e.g., toward the second plurality of optical ports 112) via second plurality of tap couplers optically coupled (e.g., evanescent coupling) to the second plurality of bus optical waveguides 104. In some instances, the second plurality of tap couplers may be located at the second plurality of optical ports 112 (“B1”...“B”). nThe optical switch is optically coupled to a second plurality of bus optical waveguides 104 at a position between the first plurality of bus optical waveguides 102 and the corresponding optical switch. The optical switch is configured to reroute light between the corresponding one in the first plurality of bus optical waveguides 102 and the second plurality of bus optical waveguides 104. In some cases, each of the first plurality of tap couplers can couple 1% to 5% of the light propagating in the corresponding bus optical waveguide in the first and second plurality of bus optical waveguides 102, 104 to the mPD, and the mPD is coupled to the end of the tap coupler opposite the other end coupled to the bus optical waveguide.

[0230] In some embodiments, the first and second plurality of mPDs 1704a, 1704b may be electrically coupled to electronic circuit 1708 to convert the first and second plurality of sensor signals (mPDA1...A) generated by the first and second plurality of mPDs 1704a, 1704b respectively. m and mPD B1...B m (Also known as detector signals) are provided to electronic circuitry 1708. In some embodiments, electronic circuitry 1708 may process first and second plurality of detector signals (mPD A1...A) m and mPD B1...B m This is used to detect and locate faulty or defective optical switches in the IOCS device 1701. In some embodiments, the electronic circuit 1708 may additionally receive an indication of activation signals provided to the optical switches of the IOCS device 1701 and use these signals to detect and locate faulty optical switches. In some embodiments, the activation signal is an electrical signal provided to a MEMS actuator of the optical switch to movably couple a shunt waveguide of the optical switch to one or more bus optical waveguides. In some embodiments, the indication of activation signals provided to the optical switches may include a portion of the actuation signal or its amplitude or phase indicating an indicator signal (e.g., a digital signal) provided to the optical switches. In some instances, the indicator signal or the port from which the indicator signal is received may include the position of the optical switch relative to the optical switch matrix and / or bus optical waveguides of the IOCS device 1701. For example, the electronic circuit 1708 may receive a signal indicating that activation signals are provided to a first optical switch to reroute light received from a first port or a first plurality of optical ports 106 from a first bus optical waveguide in a first plurality of bus optical waveguides 102 to a second bus optical waveguide in a second plurality of bus optical waveguides 104. Furthermore, electronic circuit 1708 may receive a first sensor signal from the first mPD of the second plurality of mPDs 1704a, indicating the amount of light (e.g., optical power) coupled from the first bus optical waveguide to the second bus optical waveguide, and in response to determining that the first sensor signal is below a signal threshold (indicating that the optical power rerouted by the optical switch is below a power threshold), electronic circuit 1708 may generate a warning signal.

[0231] In some embodiments, the IOCS device may include an mPD configured to receive and monitor light output from an output optical port and / or an mPD configured to receive and monitor light supplied through an optical port of the same bus optical waveguide located at an end region of the bus optical waveguide.

[0232] Figure 17B schematically illustrates a top view of another exemplary IOCS device 1702 including multiple mPDs for monitoring light propagating in multiple bus optical waveguides. In various embodiments, IOCS device 1702 may include one or more features described above relative to IOCS device 1701. Similar to IOCS device 1701, IOCS device 1702 includes first and second multiple bus optical waveguides 102, 104 terminated at first and second multiple optical ports 106, 112, multiple optical switches for controllably optically coupling individual of the first multiple waveguides 102 to individual of the second multiple waveguides 104, and first and second multiple mPDs 1704a, 1704b coupled to the first and second multiple bus optical waveguides 104, 102 at locations between the first and second multiple optical ports 106, 112 and the corresponding optical switches. As described above, the first and second plurality of mPDs 1704a, 1704b can detect portions of light coupled from the first plurality of bus optical waveguides to the second plurality of bus optical waveguides, and vice versa. In some embodiments, in addition to the first and second plurality of mPDs 1704a, 1704b, the IOCS device 1702 may also include mPDs configured to monitor optical power passing through optical switches (not rerouted by the optical switches). For example, the IOCS device 1702 may include a third plurality of mPDs 1706a configured to receive light from end regions (e.g., waveguide ends) of the first plurality of bus optical waveguides 102 and a fourth plurality of mPDs 1706b configured to receive light from end regions (e.g., waveguide ends) of the second plurality of bus optical waveguides 104. For example, the third plurality of mPDs 1916 can be mated and coupled to the bus optical waveguide 102 of the first plurality of bus optical waveguides terminated at the optical ports of the first plurality of optical ports 106 via the end region of the bus optical waveguide opposite to the optical port. The portion of light that the mPD can receive is input to the bus optical waveguide (via the optical port) and transmitted directly to the mPD without coupling or rerouting to the waveguide in the second plurality of bus optical waveguides 104. In some embodiments, the first, second, third, and fourth plurality of mPDs 1704a, 1704b, 1706a, and 1706b may be electrically connected to electronic circuit 1708, which is configured to receive first, second, third, and fourth detector signals (mPD A1…Am, mPD B1…Bm, mPD C1…Cm, mPD D1…Dm) from the first, second, third, and fourth plurality of mPDs 1704a, 1704b, 1706a, and 1706b and use the first, second, third, and fourth detector signals to determine the state or functionality of the optical switch of IOCS device 1702.For example, a first detector signal received from one of the first plurality of mPDs 1704a may indicate the amount of light rerouted by the optical switch, and a fourth detector signal received from one of the fourth plurality of mPDs 1706b may indicate the amount of light not rerouted by the optical switch. In some embodiments, the electronic circuit 1708 may use one or both of the first and second plurality of detector signals to determine the on / off state of the optical switch. Furthermore, in some embodiments, the electronic circuit may use both the first and second signals to determine the ratio of light coupled by the optical switch to light transmitted through the optical switch (uncoupled). In some such embodiments, determining this ratio may allow the electronic circuit 1708 to determine modifications to the activation signal to increase the ratio above a threshold level. Advantageously, monitoring the amount of light coupled by the optical switch and the amount of light transmitted through the optical switch (light not coupled to the optical switch and / or rerouted by the optical switch) may be used to determine the efficiency of the optical switch and / or the displacement of the shunt waveguide of the optical switch relative to the corresponding bus optical waveguide (e.g., vertical displacement of the coupling end).

[0233] Figure 17C schematically illustrates a top view of another exemplary IOCS device 1703 including multiple in-line mPDs for monitoring light propagating in multiple bus optical waveguides. In various embodiments, IOCS device 1703 may include one or more features described above with respect to IOCS device 1702 and / or IOCS device 1703. Similar to IOCS devices 1701, 1702, IOCS device 1703 includes first and second multiple waveguides 102, 104 terminated at first and second multiple optical ports 106, 112, multiple optical switches for controllably optically coupling individual of the first multiple waveguides 102 to individual of the second multiple waveguides 104, and multiple mPDs directly optically coupled to the first and second multiple bus optical waveguides 104, 102 at locations between the first and second multiple optical ports 106, 112 and the corresponding optical switches. In some embodiments, the plurality of mPDs of the IOCS device 1703 include first and second plurality of in-line mPDs 1710a and 1710b monolithically integrated with the first and second plurality of bus optical waveguides 102 and 104, respectively. In some such embodiments, the in-line mPDs of the first and second plurality of in-line mPDs 1710a and 1710b may include portions of the in-line mPD optically coupled thereto to receive light from the bus optical waveguide. In some embodiments, individual mPDs may be located near the end of the bus optical waveguide closer to the optical port. In some embodiments, the in-line mPDs of the first and second plurality of in-line mPDs 1710a and 1710b may include reverse-biased photodiodes (e.g., reverse-biased pin photodiodes). In some instances, when the in-line mPD includes a pin photodiode, the intrinsic region of an individual mPD may include the region of the in-line mPD optically coupled thereto to receive light from the bus optical waveguide (e.g., the end region closer to the optical port). When a reverse bias is applied to the p and n regions, free carriers (electrons and holes) generated from light in the bus optical waveguide can sweep across the p and n regions, resulting in a current change through the pin diode proportional to the optical power propagating in the bus optical waveguide. In some embodiments, the propagation of light in the in-line mPD can generate electron-hole pairs via two-photon absorption (e.g., two-photon absorption in silicon) or defect / interface state-assisted absorption. In some cases, these photogenerated electron-hole pairs (free carriers) can be moved by the reverse-biased pn junction to generate a photocurrent.

[0234] In some embodiments, similar to IOCS device 1702, IOCS device 1703 may further include, in addition to the first and second plurality of mPDs 1710a, 1710b, an mPD configured to monitor optical power through an optical switch (not redirected by the optical switch). These additional mPDs may include one or more features described above with respect to the third and fourth plurality of mPDs 1706a, 1706b, for example, they may be configured to receive light from waveguide end regions of the first and second plurality of bus optical waveguides 102, 104, respectively, opposite the first and second plurality of optical ports 106, 112. In some embodiments, these additional mPDs may be dockably coupled to the end regions of the bus optical waveguides opposite the optical ports or may be monolithically integrated with the end regions, such that individual mPDs include the end regions of the bus optical waveguides to which the individual mPDs optically connected to the optical ports of the bus optical waveguides are optically coupled (similar to the first and second plurality of mPDs 1706a, 1706b).

[0235] In some embodiments, one or more of the mPDs used to monitor the IOCS device may be external photodetectors that receive light from a bus optical waveguide via an optical port or waveguide facet. In some such embodiments, these external mPDs may be mounted, coupled, or otherwise integrated onto a carrier chip along with the IOCS device.

[0236] As described above, in some embodiments, the IOCS device may include an electrical or electromechanical sensor configured to directly monitor an optical switch. In some instances, the electrical or electromechanical sensor may be used to generate a sensor signal indicating displacement of a shunt optical waveguide (e.g., an end region of the shunt optical waveguide) relative to a bus optical waveguide, to which the optical switch is controllably optically coupled. In some embodiments, the electrical or electromechanical sensor may include a capacitive sensor having at least one movable conductive plate mechanically coupled to the shunt optical waveguide (e.g., via a structure supporting the shunt optical waveguide). In some such embodiments, the electromechanical sensor may be integrated with the optical waveguide. In some embodiments, at least a portion of the electromechanical sensor may be co-fabricated with the bus optical waveguide or the optical switch. In some instances, the capacitive sensor may include a fixed conductive plate formed on or within a substrate or waveguide layer forming the bus optical waveguide and a movable conductive plate formed on a structure mechanically supporting a movable region of the shunt optical waveguide. In some instances, one or both of the fixed and movable conductive plates may include portions of an electromechanical actuator configured to move the end region of the shunt optical waveguide. For example, identical conductive plates on one or both ends of a shunt waveguide with electromechanical force applied can be used to detect and measure movement and displacement of the shunt optical waveguide. In some embodiments, a capacitive sensor integrated with an optical switch may include a pair of capacitors mechanically coupled to one of the end regions of a corresponding shunt optical waveguide. In some such embodiments, the capacitance of each capacitor in the capacitor pair may indicate the mechanical displacement of one of the two end regions of the shunt optical waveguide relative to the bus optical waveguide. This capacitive sensor can be used to generate two sensor signals, each indicating the mechanical displacement of one of the end regions.

[0237] Figure 18 schematically illustrates a top view of an exemplary IOCS device 1800 including an optical switch with an integrated capacitive sensor 1804, wherein individual capacitive sensors (not shown) are used to monitor the state (e.g., on / off state) of individual optical switches. For example, the capacitive sensor may be electrically connected to electronic circuitry that uses the capacitive sensor to generate a sensor signal indicating the displacement of the corresponding shunt optical waveguide. In some instances, the electronic circuitry may measure the capacitance of the capacitive sensor and generate a sensor signal proportional to the measured capacitance. In some instances, the electronic circuitry may include one or more features described above with respect to electronic circuitry 1708 described above with respect to IOCS device 1701. For example, the electronic circuitry (not shown) may use a capacitive sensor to generate multiple sensor signals indicating the state (e.g., on / off state) and / or performance of the optical switches of IOCS device 1703. In some embodiments, IOCS device 1800 may include one or more features described above with respect to IOCS device 200 (Figure 2A).

[0238] In some cases, the coupling gap (e.g., vertical distance) between the shunt optical waveguide and the corresponding bus optical waveguide of the optical switch may be less than a threshold in the on state and greater than a threshold in the off state. The electronic circuitry can use a capacitive sensor integrated with the optical switch to measure the magnitude of the coupling gap and compare the measured value of the coupling gap with the threshold to determine the measurement state of the shunt optical waveguide. In some cases, in response to detecting a difference between the measured state of the shunt optical waveguide and its expected state (e.g., based on the presence or absence of an indication provided to the optical switch for activation), the electronic circuitry can determine that the optical switch has failed.

[0239] As described above, in some embodiments, a pair of photodetectors or capacitive sensors may generate, or be used to generate, a sensor signal indicating the ratio between the amount of light rerouted by the optical switch and the amount of light received by the optical switch from the bus optical waveguide. In some instances, this ratio may be referred to as the efficiency of the optical switch. In some instances, the first photodetector in the photodetector pair may generate a first sensor signal indicating the amount of light rerouted by the optical switch, and the second photodetector may generate a second sensor signal indicating the amount of light passing through the optical switch or the corresponding switching unit (not rerouted), and electronic circuitry (e.g., electronic circuitry 1708) may determine the efficiency of the optical switch by electronically processing the first and second sensor signals. In some instances, the electronic circuitry may use a capacitive sensor to determine the efficiency of the optical switch based at least in part on the capacitance of the capacitive sensor and a predetermined relationship between the capacitance and the efficiency of the optical switch.

[0240] Therefore, in some cases, sensor signals generated by capacitive sensors or by a pair of photodetectors or a single capacitive sensor can be used by electronic circuitry to determine the on / off state of the corresponding optical switch by determining whether the efficiency of the optical switch is higher or lower than a threshold associated with the on / off state. In some cases, in response to determining that the efficiency of the optical switch is lower than the threshold or higher than the threshold but lower than the desired value, the electronic circuitry can change the actuation signal provided to the optical switch to improve the efficiency of the optical switch or change the state of the switch.

[0241] In some embodiments, the mPD of the IOCS can monitor the output power at multiple optical ports, and the electronic circuitry can compare the detected output power level with the desired output power level and determine that the optical switch has failed in response to detecting that the difference between the detected output power level and the desired output power level is greater than a tolerance threshold.

[0242] In some embodiments, a pair of photodetectors or a capacitive sensor may generate or be used to generate sensor signals indicating the location of a failed optical switch within the network of optical switches. For example, a first photodetector in a photodetector pair may generate a first sensor signal indicating the amount of light rerouted by the failed optical switch, and a second photodetector may generate a second sensor signal indicating the amount of light passing through the failed optical switch or its corresponding switching unit (not rerouted), and electronic circuitry (e.g., electronic circuitry 1708) may use the first and second sensor signals to determine the location of the failed optical switch relative to a waveguide cross-junction of the optical switch network. In some instances, a capacitive sensor may be identified by the electronic circuitry based on an electrical port of the electronic circuitry, through which the capacitive sensor is connected. In such instances, the electronic circuitry may determine the location of the failed optical switch relative to a waveguide cross-junction of the optical switch network by identifying a capacitive sensor integrated with the optical switch.

[0243] In some embodiments, when the input light is provided to the bus optical waveguide through the optical port and none of the optical switches along the bus optical waveguide are in the ON state, the amount of optical power received by the mPD located at the end region of the bus optical waveguide (e.g., dock-coupled to the waveguide) can be greater than 90%, greater than 95%, greater than 98%, or greater than 99% of the power of the input light coupled to the bus optical waveguide. When one of the optical switches along the bus optical waveguide is ON, the amount of optical power received by the mPD located at the end region of the bus optical waveguide can be less than 70%, less than 60%, less than 50%, less than 30%, less than 10%, or less than 5% of the power of the input light coupled to the bus optical waveguide. In some embodiments, when an actuation signal is provided to at least one optical switch along the bus optical waveguide (e.g., a MEMS actuator with voltage applied to the optical switch) to put at least one optical switch in the ON state and a sensor signal generated by the mPD at the end of the bus optical waveguide indicates that the optical power level is greater than 90% of the power of the input light coupled to the bus optical waveguide, the electronic circuit can receive the indication provided by the actuation signal to at least one optical switch and the sensor signal generated by the mPD to determine that at least one optical switch has failed or malfunctioned because it was in the OFF state after receiving the actuation signal.

[0244] In some embodiments, when no actuation signal is provided to any of the optical switches along the bus optical waveguide (e.g., a MEMS actuator with voltage applied to the optical switch) to put at least one optical switch in the ON state and a sensor signal generated by the mPD at the end of the bus optical waveguide indicates that the optical power level is less than 70% of the power of the input light coupled to the bus optical waveguide, the electronic circuit can receive the sensor signal generated by the mPD and determine that at least one optical switch has failed or malfunctioned if no actuation signal is provided to one of the optical switches along the bus optical waveguide, since it is in the ON state without receiving an actuation signal.

[0245] In various embodiments, if the mPD receives sensor signals from light rerouted (or coupled) by optical switches along the bus optical waveguide, configured to receive such light, the user or electronic circuitry cannot determine which of the plurality of optical switches along the bus optical waveguide has failed or malfunctioned. Advantageously, in embodiments where the IOCS includes an mPD configured to receive light rerouted (or coupled) by optical switches and light passing through optical switches (e.g., IOCS device 1702), the user or electronic circuitry can determine the location of the failed optical switch relative to the waveguide cross junction of the optical switch network.

[0246] In various applications, the sensor configurations described above with respect to IOCS devices 1701, 1702, and 1703 can be integrated with the optical waveguides and optical switches of the IOCS device, which includes a single waveguide layer formed on a single wafer, two waveguide layers formed on a single wafer, a waveguide layer formed on a wafer and a waveguide layer suspended above the wafer, and two bonded wafers each comprising one of a pair of waveguide layers separated by a gap. For example, the sensor configurations described above with respect to IOCS devices 1701, 1702, and 1703 can be integrated with IOCS devices 200, 201, 600, or 700. In some cases, these sensor configurations can communicate with electronic circuitry (e.g., electronic processing circuitry) configured to monitor the optical switch based on one of the methods described above. Additionally, in some cases, the electronic circuitry can control one or more actuation signals provided to the optical switch based at least in part on one or more sensor signals received from one or more sensors in the sensor configuration.

[0247] In some embodiments, the IOCS (e.g., a chip or substrate including the IOCS) may be integrated, mounted, bonded, or otherwise electrically connected to a chip including electronic circuitry (e.g., an integrated circuit IC) configured to monitor and / or drive an optical switch of the IOCS. In some instances, the electronic circuitry may include CMOS circuitry 1802 (e.g., CMOS circuitry fabricated on a wafer or chip separate from the IOCS 1800). In the example shown in FIG. 18, the IOCS device 1800 is integrated with CMOS circuitry 1802, which is electrically connected to and configured to use a capacitive sensor of the IOCS device 1800 to monitor the state of the optical switch in the IOCS device 1800. In some embodiments, CMOS circuitry 1802 may be further configured to control the state of the optical switch. In some embodiments, the actuator of the optical switch may include a capacitive sensor (e.g., an actuation conductive plate may act as a conductive plate of a capacitor). In some embodiments, the IOCS 1800 may be electrically connected and bonded to the CMOS circuitry 1802 via a plurality of solder balls. In some instances, the CMOS circuit 1802 may include an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA).

[0248] IOCS device with recovery optical waveguide

[0249] In some embodiments, the IOCS may include recovery optical switches and recovery optical waveguides configured to establish a recovery optical path in the event of failure of one or more optical switches of the IOCS. In some such embodiments, in response to determining that an optical switch has failed, is ineffective, or is defective, the electronic circuitry may establish a recovery optical path that bypasses or avoids the failed optical switch to maintain or provide optical connectivity between two optical ports that would otherwise be optically connected by the failed optical switch. In some instances, the electronic switch may establish a recovery optical path via the recovery optical waveguide of the IOCS by generating one or more recovery activation signals that activate one or more recovery optical switches, which are configured to controllably optically couple the recovery optical waveguide to a bus optical waveguide connected to the two optical ports.

[0250] Figure 19A schematically illustrates a top view of an IOCS device 1900 having two bus optical waveguides 102a and 104a for bypassing a primary optical switch 1904a and first and second recovery optical switches 1906a and 1905a. In some embodiments, the IOCS device 1900 may include a first bus optical waveguide 102a formed on or above a substrate (e.g., in a first waveguide layer formed on the substrate) and a second bus optical waveguide 104a formed above the substrate (in a first waveguide layer or a second waveguide layer vertically separated from the first waveguide layer) and a primary optical switch 1904a controllably optically coupling the first and second optical waveguides 102a and 104a. In some embodiments, a first bus optical waveguide 102a may extend from a first optical port 106a near a first edge of the IOCS device 1900 along a first direction (e.g., generally parallel to the x-axis) away from the first edge, and a second bus optical waveguide may extend from a second optical port 112a near a second edge of the IOCS device 1900 along a second direction (e.g., generally parallel to the y-axis) away from the second edge. In some cases, the first and second directions may be generally perpendicular; however, the embodiments are not limited thereto, and the angle between the first and second directions may have any value.

[0251] In some instances, the primary optical switch 1904a may be activated by a first activation signal provided by electronic circuitry 1708. In some embodiments, the primary optical switch 1904a may include a first shunt optical waveguide configured to move from an off state relative to the first and second optical waveguides 102a, 104a to an on state when activated by the first activation signal. In the off state, the first shunt optical waveguide is optically decoupled from at least one of the first and second bus optical waveguides 102a, 104a, and in the on state, the first shunt optical waveguide optically couples the first bus optical waveguide 102a and the second bus optical waveguide 104a to redirect light from the first bus optical waveguide 102a to the second bus optical waveguide 104a, or vice versa.

[0252] In some embodiments, the integrated optical circuit may include a recovery optical waveguide 1902a configured to, for example, establish a recovery optical path between the first and second bus optical waveguides 102a, 104a when an optical path between the first and second bus optical waveguides cannot be established by the primary optical switch 1904a and through the first shunt optical waveguide therein. In some embodiments, the recovery optical waveguide 1902a may be controllably optically coupled to the first bus optical waveguide 102a via a first recovery optical switch 1905a and controllably optically coupled to the second bus optical waveguide 104a via a second recovery optical switch 1906a. In some embodiments, the recovery optical waveguide 1902a may extend from a first end near the first bus optical waveguide 102a (e.g., between the first optical port 106a and the primary optical switch 1904a) to a second end near the second bus optical waveguide 104a (e.g., between the second optical port 112a and the primary optical switch 1904a). In some embodiments, the recovery optical waveguide 1902a may extend from a first end near a first edge of the IOCS device 1900 to a second end near a second edge of the IOCS device 1900 to cross the first bus optical waveguide 102a at a first crossing region (e.g., between the first optical port 106a and the primary optical switch 1904a) and the second bus optical waveguide 104a at a second crossing region (e.g., between the second optical port 112a and the primary optical switch 1904a). In some instances, the first and second edges may extend in two generally perpendicular directions; however, embodiments are not limited thereto and other configurations are possible. In some embodiments, the recovery optical waveguide 1902a may include at least one bending region. In some cases, the first and second crossing regions may be configured to prevent cross-coupling of light between the first or second bus optical waveguides 102a, 104a and the recovery optical waveguide 1902a.

[0253] In some embodiments, the first recovery optical switch 1904a may include a second shunt optical waveguide configured to move from an off state relative to the first bus optical waveguide 102a and the recovery optical waveguide 1902a to an on state when activated by a second activation signal received from electronic circuitry 1708. In the off state, the second shunt optical waveguide is optically decoupled from at least one of the first bus optical waveguide 102a and the recovery optical waveguide 1902a, and in the on state, the second shunt optical waveguide optically couples the first bus optical waveguide 102a and the recovery optical waveguide 1902a to redirect light from the first bus optical waveguide 102a to the recovery optical waveguide 1902a, or vice versa. In some embodiments, a first recovery optical switch 1905a may be formed between a first optical port 106a and a primary optical switch 1904a, wherein a first bus optical waveguide 102a and a recovery optical waveguide 1902a are close to or intersect each other, such that a second shunt optical waveguide may be configured to couple the first bus optical waveguide 102a to the recovery optical waveguide 1902a.

[0254] In some embodiments, the second recovery optical switch 1906a may include a third shunt optical waveguide configured to move from an off state relative to the second bus optical waveguide 104a and the recovery optical waveguide 1902a when activated by a third activation signal received from electronic circuitry 1708. In the off state, the third shunt optical waveguide is optically decoupled from at least one of the second bus optical waveguide 104a and the recovery optical waveguide 1902a, and in the on state, the third shunt optical waveguide optically couples the second bus optical waveguide 104a and the recovery optical waveguide 1902a to redirect light from the second bus optical waveguide 104a to the recovery optical waveguide 1902a, or vice versa. In some embodiments, a second optical switch 1906a may be formed between a second optical port 112a and a primary optical switch 1904a, wherein a second bus optical waveguide 102a and a recovery optical waveguide 1902a are close to or cross each other, such that a third shunt optical waveguide may be configured to couple the second bus optical waveguide 104a to the recovery optical waveguide 1902a.

[0255] In various embodiments, electronic circuitry 1708 may be configured to monitor primary optical switch 1904a to determine the on / off state of primary optical switch 1904a. In some embodiments, electronic circuitry 1708 may receive at least a first sensor signal (detector signal) from a first monitoring sensor configured to monitor the on / off state of primary optical switch 1904a. In various embodiments, the monitoring sensor may include a capacitive sensor integrated with primary optical switch 1904a or a photodetector optically coupled to one or both of the first and second bus optical waveguides 102a, 104a. In various embodiments, the first monitoring sensor may include one or more features described above with respect to IOCS devices 1701, 1702, 1703, and 1800 and may be integrated with the first and second bus optical waveguides 102a, 104a and primary optical switch 1904a based on any of the configurations described above with respect to IOCS devices 1701, 1702, 1703, and 1800.

[0256] For example, the first monitoring sensor may include one or both of a first photodetector 1912a that receives light from an end of a first bus optical waveguide 102a opposite to a first optical port 106a and a photodetector 1914a that receives light from an end of a second bus optical waveguide 104a opposite to a second optical port 112a. In various embodiments, one or both of the first and second photodetectors 1912a, 1914a may be fabricated, disposed, or bonded thereto to a substrate on which the first and second bus optical waveguides 102a, 104a are fabricated; however, embodiments are not limited thereto and in some cases, one or both of the first and second photodetectors 1912a, 1914a may be external photodetectors configured (e.g., optically aligned) to receive light from the first and second bus optical waveguides 102a, 104a.

[0257] In some embodiments, electronic circuitry 1708 can control the on / off state of primary optical switch 1904a by generating a first activation signal (e.g., based on a control signal received from another electronic circuit). In some embodiments, electronic circuitry 1708 may receive an indication of the first activation signal provided to primary optical switch 1904a by another electronic circuit. In some embodiments, electronic circuitry 1708 may be configured to determine, for example, the desired state of the on / off switch based on a signal received from another electronic circuit. In some instances, the signal may be the first activation signal or a signal indicating that the first activation signal is provided to primary optical switch 1904a.

[0258] In some embodiments, electronic circuitry 1708 can control the on / off states of the first and second recovery optical switches 1905a and 1906a by generating second and third activation signals. Additionally, in some embodiments, electronic circuitry 1708 can be configured to monitor the first and second recovery optical switches 1905a and 1906a to determine their on / off states. In some embodiments, electronic circuitry 1708 can receive second and third sensor signals from second and third monitoring sensors configured to monitor the on / off states of the first and second recovery optical switches 1905a and 1906a, respectively. In various embodiments, the monitoring sensors may include a capacitive sensor integrated with the primary optical switch 1904a or a photodetector optically coupled to one or both of the first and second bus optical waveguides 102a and 104a. In various embodiments, the second and third monitoring sensors may include one or more features described above with respect to IOCS devices 1701, 1702, 1703 and 1800 and may be integrated with the first and second bus optical waveguides 102a, 104a and the primary optical switch 1904a based on any of the configurations described above with respect to IOCS devices 1701, 1702, 1703 and 1800.

[0259] For example, the second and third monitoring sensors may include third and fourth photodetectors 1916a and 1918a that receive light from the first and second ends of the recovery optical waveguide 1902a, respectively. In various embodiments, one or both of the third and fourth photodetectors 1916a and 1918a may be fabricated, disposed, or bonded to a substrate on which the first and second bus optical waveguides 102a and 104a are fabricated; however, embodiments are not limited thereto and in some cases, one or both of the third and fourth photodetectors 1916a and 1918a may be external photodetectors configured (e.g., optically aligned) to receive light from the recovery optical waveguide 1902a.

[0260] In some embodiments, in response to receiving one or more sensor signals, electronic circuitry 1708 may generate second and third activation signals and provide them to first and second recovery optical switches 1904a and 1906a to activate the first and second recovery optical switches 1904a and 1906a and establish a recovery path between the first and second bus optical waveguides 102a and 104a. In some cases, one or more sensor signals may indicate a failure of the primary optical switch 1904a. In some instances, electronic circuitry 1708 may include processing circuitry 1708a and driver circuitry 1708b. Processing circuitry 1708a may receive one or more sensor signals from one or more monitoring sensors, process the sensor signals to determine that the first recovery optical switch 1905a has failed, and in response to this determination, cause driver circuitry 1708b to generate second and third activation signals and provide them to the first and second recovery optical switches 1904a and 1906a to establish a recovery path. In various implementations, the driver circuit 1708b may provide the second and third activation signals to the first and second recovery optical switches 1904a, 1906a substantially simultaneously or at different times (e.g., sequentially).

[0261] In some instances, electronic circuitry 1708 may receive an indication provided to primary optical switch 1904a by a first activation signal (e.g., by another electronic circuit) or otherwise determine the expected on state of primary optical switch 1904a, determine the current on / off state associated with primary optical switch 1904a based on a first sensor signal, and activate first and second recovery optical switches 1905a, 1906a to establish a recovery optical path in response to detecting a difference between the expected and current states of primary optical switch 1904a.

[0262] In some embodiments, once the first and second recovery optical switches 1905a and 1906a are activated, the electronic circuit 1708 can use the second and third sensor signals associated with the first and second recovery optical switches 1905a and 1906a to determine that the first and second recovery optical switches 1905a and 1906a are activated and that a recovery optical path has been established by the recovery optical waveguide 1902a.

[0263] In various embodiments, bus optical waveguides 102a, 104a and primary optical switch 1904a may be bus optical waveguides of the first and second plurality of bus optical waveguides 102, 104, and optical switches and recovery optical waveguides 1902a and first and second recovery optical switches 1906a, 1905a of any of the IOCS devices 200, 201, 202, 203, 1701, 1702, 1703 or 1800 may be formed on any of these IOCS devices to establish a recovery optical path for bypassing the optical switches.

[0264] In various applications, the IOCS device 1900 may include a single waveguide layer formed on a single wafer, two waveguide layers formed on a single wafer, a waveguide layer formed on a wafer and a waveguide layer suspended above the wafer, and two bonded wafers each comprising one of a pair of waveguide layers separated by a gap. In some embodiments, the first and second bus optical waveguides 102a, 104a and the recovery optical waveguide 1902a may be formed in a single waveguide layer on a substrate. In some embodiments, the IOCS device 1900 may include one or more features described above with respect to IOCS device 600 or IOCS device 700. For example, a first segment of the first optical waveguide 102a and the recovery optical waveguide 1902a may be formed in a first waveguide layer and a second segment of the second optical waveguide 104a and the recovery optical waveguide 1902a may be formed in a second waveguide layer vertically separated from the first waveguide layer.

[0265] In some embodiments, one or more of photodetectors 1916a, 1912a, 1918a, and 1918a may be external photodetectors that receive light from a bus optical waveguide via a waveguide facet near the edge of the IOCS device 1900. In some such embodiments, these external photodetectors may be mounted, coupled, or otherwise integrated onto a carrier chip together with the IOCS device.

[0266] Figure 19B schematically illustrates a top view of an exemplary IOCS device 1901 having a recovery optical waveguide formed in a single waveguide layer (e.g., a waveguide layer formed on a substrate) and recovery optical switches for establishing a recovery optical path via the recovery optical waveguide. In some embodiments, the IOCS device 1901 may include a first plurality of bus optical waveguides 102 extending from a first plurality of optical ports 106 (A1...Am) to a first plurality of mPDs 1912 (mPD A1...mPD Am), a second plurality of bus optical waveguides 104 extending from a second plurality of optical ports 112 (B1...Bn) to a second plurality of mPDs 1914 (mPD B1...mPD Bm), and a plurality of primary optical switches 1904 formed at the intersections of the bus optical waveguides and configured to controllably optically couple individuals of the first plurality of bus optical waveguides 102 to individuals of the second plurality of bus optical waveguides 104. In some cases, individual ports may be connected (e.g., optically connected) to corresponding bus optical waveguides, and individual mPDs may be located at the ends of individual bus optical waveguides (e.g., individual mPDs may be dockably coupled to bus optical waveguides). The IOCS device 1901 may further include a plurality of recovery optical waveguides 1902 extending from a third plurality of mPDs 1916 (mPD C1...mPD Cm) to a fourth plurality of mPDs 1918 (mPD D1...mPD Dm). In some embodiments, one or more of the recovery optical waveguides 1902 may include a curved waveguide region (e.g., a 90-degree bend). In some embodiments, the first and third plurality of mPDs 1912, 1916 may be formed or disposed along a first edge of the IOCS device 1901, and the second and fourth plurality of mPDs 1914, 1918 may be formed or disposed along a second edge of the IOCS device 1902. In some instances, the first and second edges may be substantially perpendicular to each other; however, embodiments are not limited thereto, and the angle between the first and second edges of the IOCS device 1901 may be an angle other than 90 degrees. The IOCS device 1901 may include a first plurality of recovery optical switches configured to controllably optically couple a plurality of recovery optical waveguides 1902 to a first plurality of bus optical waveguides 102, and a second plurality of recovery optical switches 1906 configured to controllably optically couple the plurality of recovery optical waveguides 1902 to a second plurality of bus optical waveguides 104. In some embodiments, the plurality of primary optical switches 1904 may form a primary optical switch array 1910 (m×n array) with m rows and n columns, the first plurality of recovery optical switches 1905 may form a first recovery switch array (or matrix) 1909a (m×q array) with m rows and q columns, and the second plurality of recovery optical switches 1906 may form a second recovery optical switch array 1909b (q×n array) with q rows and n columns.In some cases, the first plurality of optical waveguides 102 and optical switch rows may extend along a first direction (e.g., the x-axis), and the second plurality of optical waveguides 104 and optical switch columns may extend along a second direction (e.g., the y-axis). In some instances, the first and second directions may be substantially perpendicular to each other; however, embodiments are not limited thereto, and the angle between the first and second directions may be an angle different from 90 degrees. In some embodiments, individual recovery optical waveguides may have m intersections with the first plurality of bus optical waveguides 102 and n intersections with the second plurality of bus optical waveguides 104, and recovery optical switches may be formed at or near each of these intersections to form the first and second recovery optical switch arrays 1909a, 1909b. In some embodiments, the recovery optical waveguides 1902 and bus optical waveguides and the first and second plurality of bus optical waveguides 102, 104 may not physically intersect each other, and the intersections may be associated with a top view (e.g., when the IOCS device 1901 is formed using two wafers similar to the IOCS device 600 or 700 described above). In some other embodiments, the recovery optical waveguide 1902 and the bus optical waveguides and the first and second plurality of bus optical waveguides 102, 104 may cross each other and the cross junctions may be configured to minimize or eliminate crosstalk between the cross optical waveguides.

[0267] In some embodiments, the first, second, third, and fourth plurality of mPDs 1912, 1914, 1916, and 1918 may be electrically connected to electronic circuitry 1708, which is configured to receive sensor signals (detector signals) from these mPDs and use the sensor signals to determine the state of a plurality of primary optical switches 1904. Electronic circuitry 1708 may be electrically connected to the plurality of primary optical switches 1904 and configured to control the on / off state of the plurality of primary optical switches 1904 by providing activation signals to individual primary optical switches. Electronic circuitry 1708 in FIG. 19B and its functions may include one or more features described above with respect to electronic circuitry 1708 electrically connected to IOCS devices 1701, 1702, 1703, and 1900.

[0268] Figure 20A schematically illustrates a top view of an exemplary IOCS device 2000 having bus and recovery optical waveguides formed in two vertically separated waveguide layers and a recovery optical switch for establishing a recovery optical path via the recovery optical waveguides. The IOCS device 2000 may include one or more features described above with respect to IOCS devices 1900, 1901, 600, and 700. In some embodiments, a first plurality of bus optical waveguides 102 (e.g., the first plurality of bus optical waveguides 102) optically connected to a first plurality of optical ports 106 may be formed on a first wafer (e.g., a first waveguide layer formed on the first wafer), and a second plurality of bus optical waveguides 104 (e.g., the second plurality of bus optical waveguides 104) optically connected to a second plurality of optical ports 112 may be formed on a second wafer (e.g., a second waveguide layer formed on the second wafer) or a second waveguide layer, wherein the second wafer and the second waveguide layer are vertically separated from the first wafer and the first waveguide layer (as shown and described above with respect to IOCS devices 600 and 700). In some such embodiments, a plurality of primary optical switches 1904 and a first and second plurality of recovery optical switches 1905, 1906 may be formed above the first wafer and may include shunt optical waveguides configured to controllably optically couple vertically separated optical waveguides formed in the first and second waveguide layers. In some embodiments, the bus optical waveguides and recovery waveguides of the IOCS device 2000 may not physically intersect each other, and the intersection point is the location where they intersect in a top view.

[0269] In one embodiment shown in FIG20A, both the first and second plurality of optical ports may be located on a second wafer or a second waveguide layer (e.g., above the first wafer). In some cases, the first plurality of optical ports 106 may be optically coupled to a first plurality of optical waveguides 102 (formed on the first wafer) via a plurality of interlayer optical couplers. In some embodiments, individual recovery optical waveguides may include a first segment formed on the first wafer (or in the first waveguide layer) and a second segment formed on the second wafer (or in the second waveguide layer), wherein the first and second segments are optically coupled via recovery interlayer optical couplers. Thus, the plurality of recovery optical waveguides may include a first plurality of recovery optical waveguide segments 1902a formed on the first wafer (or in the first waveguide layer) and a second plurality of recovery optical waveguide segments 1902b formed on the second wafer (or in the second waveguide layer), wherein the first and second plurality of optical waveguide segments 1902a, 1902b are optically coupled by a plurality of recovery interlayer optical couplers 2002.

[0270] In some instances, the interlayer optical coupler or recovery interlayer optical coupler of the IOCS device 2000 may include a grating interlayer optical coupler or a tapered waveguide interlayer optical coupler (e.g., the tapered waveguide interlayer coupler shown in Figures 11A to 11C).

[0271] Figures 20B and 20C schematically illustrate top views of the first wafer 2000a and the second wafer 2000b of the IOCS device 2000, respectively. In some embodiments, the first wafer 2000a (Figure 20B) may include a first plurality of bus optical waveguides 102, a plurality of primary optical switches 1904, a first and second plurality of recovery optical switches 1905, 1906, a first plurality of interlayer recovery optical coupler portions 2002a, a first plurality of interlayer optical coupler portions 802a, a first plurality of recovery optical waveguide segments, a first plurality of mPDs 1912 (mPD A1...mPD Am) and a third plurality of mPDs 1916 (mPD C1...mPD Cm). In some embodiments, the second wafer 2000b (FIG. 20C) may include a second plurality of bus optical waveguides 104, a second plurality of recovery optical waveguide segments 1902b, a second plurality of interlayer optical coupler portions 802a, a second plurality of interlayer recovery optical coupler portions 2002b, a second plurality of mPDs 1914 (mPD B1...mPD Bm) and a fourth plurality of mPDs 1918 (mPD D1...mPD Dm). Once the two wafers are aligned and bonded (e.g., using the manufacturing process described above with respect to FIG. 6C or 7C), the first and second plurality of interlayer optical coupler portions 802a, 802b may form a plurality of interlayer optical couplers 802 optically connecting the first plurality of bus optical waveguides 102 to the first plurality of optical ports 106, and the first and second plurality of interlayer recovery optical coupler portions 2002a, 2002b may form a plurality of interlayer recovery optical couplers 2002 optically connecting the first and second plurality of recovery optical waveguide segments 1902a, 1902b.

[0272] In some embodiments, the IOCS device 2000 may include one or more features described above with respect to the IOCS device 600, and the first and second wafers 2000a and 2000b may be used to manufacture the IOCS device 2000 based on the manufacturing process described in FIG. 6C. In some embodiments, the IOCS device 2000 may include one or more features described above with respect to the IOCS device 700, and the first and second wafers 2000a and 2000b may be used to manufacture the IOCS device 2000 based on the manufacturing process described in FIG. 7C.

[0273] Although the optical waveguides and ports of the OCIS device 2000 are fabricated on two vertically separated waveguide layers, embodiments are not limited thereto, and in some embodiments, the first and second plurality of optical ports and bus optical waveguides of the IOCS device 1901 may all be formed on a single waveguide layer. In some embodiments, the IOCS device 1901 may include a fixed waveguide layer (the fixed waveguide layer includes the first and second plurality of bus optical waveguides 102, 104 and the recovery optical waveguide 1902) formed on a substrate and a suspended waveguide layer suspended above the fixed waveguide layer, wherein the suspended waveguide layer is vertically separated from the fixed waveguide layer and mechanically supported by a plurality of conductive clamping structures. The suspended waveguide layer may include first, second and third plurality of shunt optical waveguides associated with the primary optical switch 1904, the first plurality of recovery optical switches 1905 and the second plurality of recovery optical switches 1906, respectively. In some instances, the space between the fixed waveguide layer and the suspended waveguide layer may be substantially free of material other than the plurality of conductive clamping structures. In some instances, the conductive clamping structure is not electrically connected to any electronic circuitry or conductive areas associated with sensors and actuators of the optical switch. In some embodiments, the substrate may include a silicon wafer having a silicon dioxide layer comprising a fixed waveguide layer formed thereon. In some instances, the first, second, and third plurality of shunt optical waveguides of the IOCS waveguide may include silicon nitride deposited over a sacrificial material, wherein the sacrificial material has been removed to suspend the suspended waveguide layer. In some instances, the first, second, and third plurality of shunt optical waveguides of the IOCS waveguide may include single-crystal silicon transferred from a silicon-on-insulator (SOI) substrate via flip-chip bonding.

[0274] In some embodiments, individual conductive clamping structures may be configured to clamp the longitudinal regions of individual of the first, second, and third plurality of shunt optical waveguides between corresponding end regions of the individual shunt optical waveguides. In some cases, the individual conductive clamping structures may define a vertical distance between a fixed waveguide layer and a suspended waveguide layer. In some embodiments, the plurality of conductive clamping structures may be photolithographically defined and fabricated metal pillars formed above the fixed waveguide layer and extending vertically through the suspended waveguide layer. In some embodiments, the metal pillars may be formed of aluminum, copper, or other metals. In some instances, the plurality of conductive clamping structures may further include planar metal layers connected to the opposing ends of the plurality of metal pillars.

[0275] In various implementations, any of the sensor configurations, recovery optical waveguide configurations, and recovery optical switch configurations described above with respect to IOCS devices 1701, 1702, 1703, 1800, 1900, 1901, and 2000 may be implemented on or used in IOCS devices 200, 201, 202, 203, 600, and 700.

[0276] In the various embodiments described above, the on or off state of the optical switch may include the on or off state of the shunt waveguide of the optical switch, and vice versa.

[0277] In some embodiments, the optical switches of the IOCS devices 1701, 1702, 1703, 1800, 1900, 1901 and 2000 may include the optical switches described above with respect to the switching unit (SC) 208 (Figures 3A to 3C, 4, 5A to 5B) or another type of MEMS optical switch.

[0278] In various embodiments, the actuators in the optical switches of IOCS devices 1701, 1702, 1703, 1800, 1900, 1901 and 2000 may include piezoelectric MEMS actuators.

[0279] Edge optical coupler

[0280] Figures 21A and 21B schematically illustrate an exemplary edge optical coupler 2100 or a fiber-to-chip optical coupler with back-etched surface, showing a front view (Figure 21A) and a three-dimensional view (Figure 21B). In some instances, the edge optical coupler 2100 may be configured to provide low-loss optical coupling between an optical fiber waveguide and an on-chip optical waveguide (e.g., a bus optical waveguide). In various applications, the optical fiber waveguide may include single-mode or multimode fiber configured to operate in or around 1310 nm or 1550 nm, for example. The fiber may be a single-mode fiber with a mode field diameter of 9.2 μm, a high-NA fiber with a mode field diameter of 6.5 μm or 3.2 μm, or a lens fiber with a mode field diameter of 6.5 μm or 3.2 μm; however, embodiments are not limited thereto, and other types of optical fibers with different mode field diameters may be coupled to the on-chip optical waveguide via edge optical couplers 2100, 2110, and 2120 described below.

[0281] In one embodiment, the edge coupler 2100 structure may include a top cladding layer 2102 that can be formed on the top side of a back (bottom) etched substrate 2106. In some instances, the top cladding layer 2102 may include a material that is transparent at the design wavelength of the edge coupler 2100 or within the operating wavelength range of the edge coupler 2100 (e.g., having a transparency of less than 0.01 cm⁻¹). -1 or less than 0.001 cm -1(Optical absorption coefficient). In some embodiments, the thickness h1 of the top cladding layer can be from 4 micrometers to 8 micrometers. In some embodiments, the edge coupler 2100 can be formed on the substrate of the IOCS (e.g., a silicon substrate) and can be configured to optically couple an optical fiber or another type of optical waveguide to the bus optical waveguide of the IOCS. In some embodiments, the edge coupler 2100 can include a tapered waveguide 2104 extending longitudinally from the waveguide end of the bus optical waveguide formed on the substrate (on which the IOCS is formed). In some embodiments, the lateral width of the tapered waveguide 2104 can increase from a first lateral width w1 at the edge of the substrate 2106 to a second lateral width w2 at the end of the bus optical waveguide formed on the substrate. However, embodiments are not limited thereto and in some embodiments, the first lateral width w1 can be greater than the second lateral width w2. In various instances, the tapered waveguide 2104 can taper linearly or non-linearly from the second lateral width w2 to the first lateral width w1. In some instances, w2 can be substantially equal to the lateral width of the bus optical waveguide formed on the substrate. In various embodiments, the tapered waveguide 2104 can be configured to adiabatically transform the transverse / lateral optical mode profile from the transverse / lateral optical mode profile of a first optical mode propagating in the bus optical waveguide to an optical mode profile closer to or matching the fiber or another external waveguide. Therefore, variations in the transverse width of the tapered waveguide 2104 can be configured to adiabatically transform the transverse / lateral optical mode profile between the bus optical waveguide of the IOCS and an external optical waveguide, such as an optical fiber. In some instances, w2 can be 1.1 to 1.5 times, 1.5 to 2 times, 2 to 3 times, 3 to 4 times, or greater than w1. In some embodiments, w2 can be from 100 nanometers (nm) to 300 nm and w1 can be from 400 nm to 1000 nm. In some embodiments, the tapered waveguide 2104 can comprise silicon nitride, silicon, or other materials (e.g., group III-V semiconductor materials). In some instances, the thickness of the tapered waveguide 2104 may be from 100 nm to 200 nm, from 200 nm to 300 nm, from 300 nm to 500 nm, from 500 nm to 700 nm, or any range of these values ​​or larger or smaller.

[0282] In some instances, a region of the substrate 2106 beneath the tapered waveguide may be removed to form a slit (e.g., an air-filled slit) 2103 beneath the tapered waveguide 2104 to modify the effective refractive index for light propagation within the tapered waveguide 2104. In some embodiments, the slit 2103 may extend substantially parallel to the longitudinal direction of the tapered waveguide 2104 (e.g., parallel to the y-axis). In some instances, the length of the slit 2103 (e.g., along the y-axis) may be greater than 20%, 30%, 50%, 80%, or more of the length of the tapered waveguide 2104. In some instances, the length of the slit 2103 (e.g., along the y-axis) may be substantially equal to the length of the tapered waveguide 2104.

[0283] In various implementation schemes, the lateral width w of slit 2103 s (Along the x-axis) can be from 5 micrometers to 10 micrometers, from 10 micrometers to 20 micrometers, from 20 micrometers to 30 micrometers, from 30 micrometers to 40 micrometers, from 40 micrometers to 50 micrometers, or any range greater or smaller than these values. In some embodiments, w s The second lateral width (w2) of the tapered waveguide may be greater than that of the tapered waveguide. In some embodiments, the slit 2103 may extend in a direction generally parallel to the tapered waveguide 2104 and the bus optical waveguide optically connected to the tapered waveguide 2104 (e.g., parallel to the y-axis). In some embodiments, the first tapered waveguide may be formed in a top cladding layer 2102 formed on the substrate 2106. In some embodiments, the top cladding layer 2102 may include a first dielectric material having a first refractive index. In various embodiments, the top cladding layer 2102 may include silicon dioxide or a polymer (e.g., epoxy resin) having a refractive index that allows the mode field diameter at the first end of the tapered waveguide 2104 to match the mode field diameter of an on-chip optical waveguide (e.g., a single-mode waveguide) and the mode field diameter at the second end of the tapered waveguide 2104 to match the mode field diameter of an optical fiber or another waveguide. In some embodiments, the slit 2103 formed beneath the tapered waveguide 2104 may be filled with a second dielectric material having a second refractive index. In some embodiments, the second refractive index may be lower than the refractive index of the substrate 2106. In some instances, the first and second refractive indices may be substantially equal. In some instances, the first and second dielectric materials may be substantially the same material. Figures 21C to 21D schematically illustrate a front view (21C) and a three-dimensional view (21C) of another embodiment of the optical edge coupler 2120. The optical edge coupler 2120 may include one or more features described above relative to the optical edge coupler 2100; however, the slit 2103 beneath the tapered waveguide of the optical edge coupler 2120 may be filled with a second dielectric material to form a bottom cladding layer 2108. In some embodiments, the second dielectric material may have a refractive index substantially equal to or matching the refractive index of the first dielectric material.

[0284] Figures 21E to 21F schematically illustrate a front view (21E) and a three-dimensional view (21F) of yet another exemplary optical edge coupler 2140. The optical edge coupler 2140 may include one or more features described above with respect to the optical edge coupler 2100; however, a bottom cladding layer 2110 may be formed below the tapered waveguide 2104 on the bottom surface of the top cladding layer 2102 and on the sidewall of the slit 2103. In some embodiments, the bottom cladding layer 2110 may include a second dielectric material. Thus, the bottom cladding layer 2110 may divide the internal volume of the slit 2103 into two regions with different refractive indices (e.g., corresponding to air and the second dielectric material). In some cases, the first thickness h4 (along the x-axis) of a portion of the bottom cladding layer 2110 formed on the bottom surface of the top cladding layer 2102 may be substantially equal to or different from the thickness h5 (along the y-axis) of the bottom cladding layer 2110 formed on the sidewall of the slit 2103. In some instances, h5 may be greater than h4. In various embodiments, h4 and h5 may be any range or greater or smaller, from 5 micrometers to 10 micrometers, from 10 micrometers to 20 micrometers, from 20 micrometers to 30 micrometers, from 30 micrometers to 40 micrometers, from 40 micrometers to 50 micrometers, from 50 micrometers to 100 micrometers, or formed by these values. In various embodiments, the vertical spacing (e.g., along the z-axis) between the tapered waveguide 2104 and the bottom surface of the top cladding layer 2102 may be from 1 micrometer to 2 micrometers, from 2 micrometers to 3 micrometers, from 3 micrometers to 4 micrometers, or any range or greater or smaller, formed by these values.

[0285] In various embodiments, the tapered waveguide 2104 can be configured to thermally transform the lateral optical power distribution (in a plane perpendicular to the direction of light propagation, such as parallel to the y-axis) from the narrower end of the tapered waveguide 2104 optically connected (or coupled) to the bus optical waveguide to the wider end of the tapered waveguide 2104 optically connected (or coupled) to the optical fiber (or waveguide formed on a chip), and vice versa.

[0286] In various implementation schemes, the width w of slit 2103 s (Parallel to the x-axis), the first dielectric material of the top cladding layer 2102, the second dielectric material filling or coating the slit 2103, h3 and / or h5 can be configured to improve the adiabatic transformation of the lateral optical power distribution from a distribution that matches or is closer to the distribution of the fiber (or another optical waveguide) to a distribution that matches or is closer to the distribution of the bus optical waveguide, thereby reducing the optical coupling loss associated with the optical mode mismatch between the bus optical waveguide and the fiber.

[0287] In various embodiments, one or more features (e.g., the geometry of the structure and / or the optical properties of the material) may be designed, selected or otherwise configured at least in part based on the design wavelength or operating wavelength range of the edge couplers 2100, 2120, 2140.

[0288] In some embodiments, each of the bus optical waveguide and edge couplers 2100, 2120, and 2140 may be monolithically fabricated on a common substrate, such that an external optical waveguide (e.g., a fiber optic waveguide) can be optically coupled to the bus optical waveguide with an optical efficiency greater than 5%, 10%, 20%, 50%, or higher. In some embodiments, at least a portion of the bus optical waveguide and edge couplers may be co-fabricated on a common substrate.

[0289] In various implementations, the optical ports of the aforementioned IOCS devices 200, 201, 202, 203, 600, 700, 1701, 1702, 1703, 1800, 1900, 1901 and 2000 may include edge couplers 2100, 2120 or 2140.

[0290] Edge Coupler Intermediate Layer

[0291] In various applications, receiving light from on-chip optical waveguides (e.g., bus optical waveguides) of an integrated photonic chip and / or transmitting light to said on-chip optical waveguides, and / or transmitting light to said on-chip optical waveguides, may not allow for high-density arrangement of bus optical waveguides and corresponding optical ports near the edge of the integrated photonic chip. In some embodiments, an edge coupler interposer (e.g., an fiber-to-chip interposer) may allow coupling of light between two waveguide arrays with different pitches. Such an edge coupler interposer may be positioned between an optical port array having a first pitch and formed on the integrated photonic chip and a second waveguide array having a second pitch greater than the first pitch. In some instances, the optical port array and the first waveguide array may include optical ports and bus optical waveguides of the IOCS, and the second waveguide array may include an optical fiber array. Thus, when an edge coupler interposer is used between the IOCS and the optical fiber array, the pitch of the optical fiber array does not limit the pitch of the optical port array, thereby allowing optical fiber coupling to a high-density IOCS device. In some embodiments, the first pitch of the optical ports and / or bus optical waveguides of the high-density IOCS may be 2, 3, 4, 5, or 10 times smaller than the second pitch of the fiber array coupled to the IOCS via the fiber-to-chip interposer. Figure 18 shows a top view of the integrated photonic MEMS OCS.

[0292] Figures 22A and 22B schematically illustrate a front view (22A) and a three-dimensional view (22B) of an edge coupler interposer layer 2200. The edge coupler interposer layer 2200 includes a one-dimensional (1D) first optical port (or waveguide facet) array 2201 configured for optical coupling to optical ports of a photonic chip, and a two-dimensional (2D) second optical port (or waveguide facet) array 2202 configured for optical coupling to a two-dimensional (2D) fiber array. In some embodiments, the edge coupler interposer layer 2200 may be configured to optically couple to a 1D optical port array arranged in a lateral direction (e.g., parallel to the x-axis) at the edge of the IOCS chip, and to a 2D fiber array arranged in both a lateral and vertical direction (e.g., along the z-axis). In some embodiments, the 1D optical port array of the IOCS may be a periodic array with a first pitch, and the 2D fiber array may be periodic with a second pitch in the lateral direction, wherein the second pitch is greater than the first pitch. In some embodiments, the first pitch may be equal to or less than 50% of the second pitch. Advantageously, by reducing the first pitch to half or less than half the second pitch, the edge coupler interposer 2200 can improve the bus optical density and optical switching density of the fiber-coupled IOCS device. The edge coupler interposer 2200 may further include a plurality of optical waveguides extending longitudinally (e.g., along the y-axis) from the first optical port array 2201 to the second optical port array 2202 to optically couple the first optical port array 2201 to the two-dimensional (2D) second optical port array 2202.

[0293] Referring again to Figures 22A and 22B, in some embodiments, the edge coupler may include a first waveguide facet array (e.g., a 1D array) 2201 (also referred to as a first plurality of optical ports) at a first periodic position (first pitch p1) along a first lateral direction (e.g., along the x-axis), a first longitudinal position (e.g., along the y-axis), and a common vertical position (e.g., along the z-axis), and a 2D waveguide facet array 2202 at a second longitudinal position, wherein the 2D waveguide facet array includes a second and a third 1D waveguide facet array that are vertically separated and form a 1D vertically separated waveguide facet array at a second periodic position (e.g., a second pitch p2) along the lateral direction. In some embodiments, the first and second waveguide surfaces 2201a and 2201b of the first waveguide surface array 2201 can be optically coupled to the third and fourth waveguide surfaces 2202a and 2202b of the vertically separated waveguide surfaces of the array 2202 via the first and second waveguides 2204a and 2204b, respectively. In some instances, the first and second waveguide surfaces 2201a and 2201b can be the nearest neighbor waveguide surfaces of the first waveguide surface array 2201. In some embodiments, the first pitch (p1) of the first 1D waveguide surface array 2201 can be at least twice as small as the second pitch (p2) of the vertically separated waveguide surfaces. In some embodiments, the first and second optical waveguides 2204a, 2204b may extend from a first longitudinal position to a second longitudinal position in the longitudinal direction (e.g., along the y-axis) to optically couple the first waveguide facet 2201a to the third waveguide 2202a and the second waveguide facet 2201b to the fourth waveguide facet 2202b. In some embodiments, p1 may be from 40 micrometers to 250 micrometers and p2 may be substantially twice or greater than p1.

[0294] In the example shown in Figure 22B, the 2D waveguide faceted array 2202 includes two 1D arrays or two rows; however, the embodiments are not limited thereto and the edge interposer layer, similar to the edge interposer layer 2200, may contain more rows.

[0295] In some embodiments, the vertical spacing (Lz) between the vertically separated waveguide facets of the array 2202 can be from 80 micrometers to 500 micrometers.

[0296] In some embodiments, the difference Ly between the first and second longitudinal positions may be from 10 micrometers to 100 micrometers, from 100 micrometers to 1000 micrometers, from 1 millimeter to 2 millimeters, or greater than the second longitudinal position.

[0297] Figure 22C schematically illustrates a top view of an IOCS 2220 having two sets of ports (labeled A1…Am and B1…Bn) along two different edges and two edge coupler interposers 2200a and 2200b (similar to edge coupler interposers 2200 each aligned and coupled to different ports in the port sets). In some cases, a first edge coupler interposer 2200a may be aligned to a first edge of the IOCS 2220 to optically couple to a first plurality of optical ports of the IOCS 2220 and corresponding first plurality of bus optical waveguides to a first plurality of optical fibers, and a second edge coupler interposer 2200a may be aligned to a second edge of the IOCS 2220 to optically couple to a second plurality of optical ports of the IOCS 2220 and corresponding second plurality of bus optical waveguides to a second plurality of optical fibers. In various implementations, IOCS 2220 may include one or more features described above with respect to IOCS devices 200, 201, 202, 203, 600, 700, 1701, 1702, 1703, 1800, 1900, 1901 and 2000.

[0298] Electronic connection and control

[0299] The aforementioned IOCS device can be controlled by an integrated circuit fabricated on a CMOS chip to activate the optical switch and put the optical switching unit in the on state by applying a control voltage to the MEMS actuator.

[0300] In some embodiments, the electrodes of the MEMS actuator can be connected to the corresponding output of the CMOS chip via through-silicon vias (TSVs). In some embodiments, the electrodes of the MEMS actuator can be connected to the corresponding output of the CMOS chip via through-oxide vias (TOVs) or via flip-chip bonding. In various embodiments, the TSV pathways and / or TOVs can be fabricated on either of the two wafers or substrates.

[0301] In some embodiments, the electronic circuitry and system (e.g., electronic circuitry 1708) may include a non-transitory memory storing machine-readable instructions and an electronic processor communicating with the non-transitory memory. In various embodiments, the electronic processor may be configured to execute machine instructions stored in the memory to provide the functionality described above regarding controlling optical switches, determining the state of optical switches based on sensor signals, establishing recovery optical paths to bypass faulty optical switches, and the like.

[0302] Example Implementation

[0303] Various additional exemplary embodiments of this disclosure can be described by the following examples:

[0304] Example 1

[0305] Example 1. An integrated optical circuit (IOC) comprising:

[0306] The first waveguide layer, wherein a first bus optical waveguide is formed;

[0307] The second waveguide layer, wherein a second bus optical waveguide is formed;

[0308] An optical switch comprising a shunt waveguide vertically disposed in the gap between the first and second bus optical waveguide layers and configured to movably couple the first and second bus optical waveguides when activated; and

[0309] A pair of optical alignment structures formed in the first and second waveguide layers, wherein the optical alignment structures are optically aligned within a predetermined tolerance to correspondingly align the first and second waveguide layers and the optical switch within the predetermined tolerance, such that when activated, the shunt waveguide optically couples the first and second bus optical waveguides to redirect light therebetween.

[0310] Example 2. An integrated optical circuit according to any of the above examples, wherein the pair of optical alignment structures includes a loop waveguide structure having two portions each formed in one of the first or second waveguide layers.

[0311] Example 3. The integrated optical circuit according to Example 2, wherein the first portion of the loopback waveguide structure includes two optically isolated waveguide segments and the second portion of the loopback waveguide structure includes a loopback waveguide segment configured to be optically coupled to the two optically isolated waveguide segments via two interlayer optical couplers.

[0312] Example 4. The integrated optical circuit according to Example 3, wherein the interlayer optical coupler includes a grating coupler.

[0313] Example 5. The integrated optical circuit according to Example 3, wherein the interlayer optical coupler includes a tapered waveguide coupler.

[0314] Example 6. An integrated optical circuit according to any of the above examples, wherein the pair of optical alignment structures includes a pair of alignment marks each formed in one of the first or second waveguide layers.

[0315] Example 7. An integrated optical circuit according to any of the above examples, further comprising a physical alignment structure including a protrusion extending between the first and second waveguide layers, the protrusion being mechanically engaged with an opening.

[0316] Example 8. The integrated optical circuit according to Example 7, wherein the protrusion has a hemispherical, cylindrical or rectangular shape, and the opening includes a V-shaped groove, a cylindrical hole or a rectangular hole.

[0317] Example 9. An integrated optical circuit according to any of the above examples, wherein a pair of optical alignment structures are formed therein outside the region forming the optical switch.

[0318] Example Implementation II

[0319] Example 1. A method for aligning two wafers comprising an integrated photonic device, the method comprising:

[0320] A first chip is provided, the first chip comprising:

[0321] The first waveguide layer contains a first bus optical waveguide.

[0322] An optical switch structure includes a shunt waveguide configured to movably optically couple a first bus optical waveguide to a second bus optical waveguide when activated to redirect light between the first and second bus optical waveguides.

[0323] The first of a pair of optical alignment structures, which includes a first waveguide structure;

[0324] A second chip is provided, the second chip comprising:

[0325] The second waveguide layer, wherein the second bus optical waveguide is formed, and

[0326] The second of the pair of optical alignment structures includes a second waveguide structure;

[0327] The first waveguide structure that provides optical input power to the first of the pair of optical alignment structures;

[0328] Position the second wafer relative to the first wafer, such that the second waveguide structure is positioned above the first waveguide structure;

[0329] The output optical power from the second waveguide structure is measured as the result of the optical coupling between the first and second waveguide structures.

[0330] Based on the measured output optical power, the first wafer is aligned relative to the second wafer; and

[0331] When the optical switch structure is activated, the measured output optical power is directly related to the optical coupling strength between the first and second optical waveguides.

[0332] Example 2. The method according to any of the above examples, wherein the first waveguide structure includes a pair of optically isolated waveguides and the second waveguide structure includes a loopback waveguide segment.

[0333] Example 3. The method according to any of the above examples, wherein the optical alignment structure further includes an interlayer optical coupler configured to optically couple the first and second waveguide structures.

[0334] Example 4. The method according to Example 3, wherein the interlayer optical coupler includes a grating coupler.

[0335] Example 5. The method according to Example 3, wherein the interlayer optical coupler includes a tapered waveguide coupler.

[0336] Example 6. According to the method of Example 5, aligning the first wafer relative to the second wafer based on the measured output optical power includes aligning the first wafer relative to the second wafer in a first direction.

[0337] Example 7. According to the method of Example 6, wherein the first wafer further includes a first of a second pair of optical alignment structures comprising a third waveguide structure and the second wafer includes a second of the second pair of optical alignment structures comprising a fourth waveguide structure.

[0338] Example 8. The method according to Example 7, wherein the method further comprises:

[0339] The second optical input power is provided to the third waveguide structure of the first of the pair of second optical alignment structures;

[0340] Position the second wafer relative to the first wafer, such that the fourth waveguide structure is positioned above the third waveguide structure;

[0341] The second output optical power output from the third waveguide structure is measured as the result of the optical coupling between the third and fourth waveguide structures;

[0342] The first wafer is aligned relative to the second wafer based on the measured second output optical power.

[0343] Example 9. The method according to Example 8, wherein aligning the first wafer relative to the second wafer based on the measurement of the second output optical power includes aligning the first wafer relative to the second wafer in a second direction.

[0344] Example 10. The method according to Example 9, wherein the first direction is substantially perpendicular to the first direction.

[0345] Example 11. The method according to Example 10, wherein the third waveguide structure includes a second pair of optically isolated waveguides and the third waveguide structure includes a second loop waveguide segment, and the second optical alignment structure further includes a second interlayer optical coupler configured to optically couple the third and fourth waveguide structures.

[0346] Example 12. The method according to Example 11, wherein the second interlayer optical coupler comprises a tapered waveguide coupler.

[0347] Example 13. According to the method of Example 12, wherein the first wafer further includes a first of a third pair of optical alignment structures comprising a fifth waveguide structure and the second wafer includes a second of the third pair of optical alignment structures comprising a sixth waveguide structure.

[0348] Example 14. The method according to Example 13, wherein the method further comprises:

[0349] The third optical input power is provided to the fifth waveguide structure of the first of the pair of third optical alignment structures;

[0350] Position the second wafer relative to the first wafer, such that the sixth waveguide structure is positioned above the third waveguide structure;

[0351] The third output optical power output from the fifth waveguide structure is measured as a result of the optical coupling between the fifth and sixth waveguide structures;

[0352] The first wafer is aligned relative to the second wafer based on the measured third output optical power.

[0353] Example 15. The method according to Example 13, wherein the fifth waveguide structure includes a second pair of optically isolated waveguides and the sixth waveguide structure includes a third loop waveguide segment, and the third optical alignment structure further includes a third interlayer optical coupler configured to optically couple the third and fourth waveguide structures.

[0354] Example 16. The method according to Example 15, wherein the third interlayer optical coupler includes a grating coupler.

[0355] Example Implementation III

[0356] Example 1. An integrated optical circuit (IOC) comprising:

[0357] The first waveguide layer, wherein a first bus optical waveguide is formed;

[0358] The second waveguide layer, wherein a second bus optical waveguide is formed;

[0359] An optical switch comprising a shunt waveguide vertically disposed in the gap between the first and second bus optical waveguide layers and configured to movably couple the first and second bus optical waveguides when activated; and

[0360] A pair of physical alignment structures formed on the first and second waveguide layers, wherein the physical alignment structures are physically coupled to align the first and second waveguide layers and the optical switch within a predetermined tolerance, such that when activated, the shunt waveguide optically couples the first and second bus optical waveguides to redirect light therebetween.

[0361] Example 2. An integrated optical circuit according to any of the examples above, wherein the pair of physical alignment structures includes a first and a second physical alignment structure.

[0362] Example 3. The integrated optical circuit according to Example 2, wherein the first or second physical alignment structure includes a protrusion.

[0363] Example 4. The integrated optical circuit according to Example 3, wherein the protrusion comprises a hemisphere or cylinder having a circular or rectangular cross-section.

[0364] Example 5. The integrated optical circuit according to Example 3, wherein the protrusion comprises a polymeric material.

[0365] Example 6. The integrated optical circuit according to Example 3, wherein the first or second physical alignment structure includes an opening.

[0366] Example 7. The integrated optical circuit according to Example 6, wherein the opening includes a V-shaped groove, an etched pyramid, or an etched cuboid.

[0367] Example 8. The integrated optical circuit according to Example 6, wherein the opening, the first waveguide layer, and the optical switch are formed on a first common substrate.

[0368] Example 9. The integrated optical circuit according to Example 8, wherein the protrusion and the second waveguide layer are disposed on a second common substrate.

[0369] Example 10. An integrated optical circuit according to Example 8, wherein the opening is formed in a region of the first common substrate outside the region of the first common substrate in which the optical switch is formed.

[0370] Example Implementation IV

[0371] Example 1. A method for aligning two wafers comprising an integrated photonic device, the method comprising:

[0372] A first chip is provided, the first chip comprising:

[0373] The first waveguide layer contains a first bus optical waveguide.

[0374] An optical switch structure includes a shunt waveguide configured to movably optically couple a first bus optical waveguide to a second bus optical waveguide when activated to redirect light between the first and second bus optical waveguides.

[0375] The first physical alignment structure in a pair of physical alignment structures;

[0376] A second chip is provided, the second chip comprising:

[0377] The second waveguide layer, wherein the second bus optical waveguide is formed, and

[0378] The second physical alignment structure in the pair of physical alignment structures is configured to be physically coupled to the first physical alignment structure;

[0379] Laterally align the first and second wafers to align the first physical alignment structure above the second physical alignment structure within a predetermined tolerance; and

[0380] The first and second physical alignment structures are vertically aligned such that, when activated, the shunt waveguide optically couples the first and second bus optical waveguides to redirect light between them.

[0381] Example 2. The method according to any of the above examples, wherein when activated, the first end portion of the shunt waveguide moves toward the first bus optical waveguide and the second end portion of the shunt waveguide moves toward the second bus optical waveguide.

[0382] Example 3. The method according to any of the above examples, wherein the first wafer includes an optical switch, the optical switch including the shunt waveguide and a microelectromechanical system (MEMS) actuator configured to move a movable portion of the shunt waveguide.

[0383] Example 4. The method according to any of the above examples, wherein the first or second physical alignment structure includes a protrusion.

[0384] Example 5. According to the method of Example 4, the protrusion includes a hemisphere or column having a circular or rectangular cross-section.

[0385] Example 6. The method according to Example 4, wherein the protrusion is disposed on the first or second wafer.

[0386] Example 7. The method according to Example 6, wherein the protrusion comprises a polymeric material.

[0387] Example 8. The method according to any of the above examples, wherein the first or second physical alignment structure includes an opening.

[0388] Example 9. The method according to Example 8, wherein the opening comprises a V-shaped groove, an etched pyramid, or an etched cuboid.

[0389] Example Implementation V

[0390] Example 1. A method for aligning two wafers comprising an integrated photonic device, the method comprising:

[0391] A first chip is provided, the first chip comprising:

[0392] The first waveguide layer contains a first bus optical waveguide.

[0393] An optical switch structure includes a shunt waveguide configured to movably optically couple a first bus optical waveguide to a second bus optical waveguide when activated to redirect light between the first and second bus optical waveguides.

[0394] The first physical alignment structure in a pair of physical alignment structures;

[0395] A second chip is provided, the second chip comprising:

[0396] The second waveguide layer, wherein the second bus optical waveguide is formed, and

[0397] The second physical alignment structure in the pair of physical alignment structures is configured to be physically coupled to the first physical alignment structure;

[0398] Microbeads are provided between the first and second physical alignment structures to mechanically link the first and second physical alignment structures;

[0399] Laterally align the first and second wafers to align the first physical alignment structure above the second physical alignment structure within a predetermined tolerance; and

[0400] The first and second physical alignment structures are directly coupled via the microbeads, such that when activated, the shunt waveguide optically couples the first and second bus optical waveguides to redirect light between them.

[0401] Example 2. The method according to any of the above examples, wherein when activated, the first end portion of the shunt waveguide moves toward the first bus optical waveguide and the second end portion of the shunt waveguide moves toward the second bus optical waveguide.

[0402] Example 3. The method according to any of the above examples, wherein the first wafer includes an optical switch, the optical switch including the shunt waveguide and a microelectromechanical system (MEMS) actuator configured to move a movable portion of the shunt waveguide.

[0403] Example 4. The method according to any of the above examples, wherein the first and second physical alignment structures include a first and a second opening.

[0404] Example 5. According to the method of Example 4, the opening includes a V-shaped groove, an etched pyramid, or an etched cuboid.

[0405] Example 6. The method according to any of the examples above, wherein the microbeads comprise a polymer.

[0406] Example 7. The method according to any of the examples above, wherein the microbeads have a spherical shape.

[0407] Example VI

[0408] Example 1. An integrated optical circuit (IOC) comprising:

[0409] A first waveguide layer is formed on a substrate, and a first bus optical waveguide is formed in the first waveguide layer;

[0410] The second waveguide layer, wherein a second bus optical waveguide is formed;

[0411] An optical switch comprising a shunt optical waveguide vertically disposed in a gap between the first and second bus optical waveguide layers and configured to movably optically couple the first and second bus optical waveguides when activated to redirect light between the first and second bus optical waveguides; and

[0412] Multiple vertical pathways, which act as mechanical anchors and electrical connections between the first and second waveguide layers to securely suspend the second waveguide layer above the first waveguide layer, are formed of a material selectively etched relative to sacrificial material removed from the gap during manufacturing.

[0413] Example 2. An integrated optical circuit according to any of the above examples, wherein an anchor of a plurality of anchors extends vertically from the first waveguide layer to the second waveguide layer, the anchor having a cross-sectional area of ​​less than 100 square micrometers.

[0414] Example 3. The integrated optical circuit according to Example 2, wherein the anchor does not include a joint interface or discontinuity from the first waveguide layer to the second waveguide layer.

[0415] Example 4. An integrated optical circuit according to any of the examples above, wherein the shunt optical waveguide is configured to be optically isolated from the first and second bus optical waveguides when the switch is in the off state and optically coupled to the first and second bus optical waveguides when the optical switch is in the on state.

[0416] Example 5. An integrated optical circuit according to any of the examples above, wherein the substrate comprises a wafer.

[0417] Example 6. An integrated optical circuit according to any of the above examples, wherein the second waveguide layer consists of a support layer on which the second bus optical waveguide is formed.

[0418] Example 7. An integrated optical circuit according to any of the examples above, wherein the thickness of the second waveguide layer is less than 800 micrometers.

[0419] Example 8. An integrated optical circuit according to any of the examples above, wherein the shunt optical waveguide is mechanically supported by a clamping structure.

[0420] Example 9. The integrated optical circuit according to Example 8, wherein the space between the first waveguide layer and the shunt optical waveguide is substantially free of material other than the plurality of anchors and the clamping structure.

[0421] Example 10. An integrated optical circuit according to any of the examples above, wherein the space between the shunt optical waveguide and the second waveguide layer is substantially free of material other than the plurality of anchors.

[0422] Example 11. An integrated optical circuit according to any of the above examples, wherein when the optical switch is in the ON state, more than 80% of the optical power propagating in the first optical waveguide is coupled to the second optical waveguide.

[0423] Example 12. An integrated optical circuit according to any of the examples above, wherein the optical switch further includes at least one microelectromechanical system (MEMS) actuator configured to actuate the shunt optical waveguide to optically couple its first end region to the first bus optical waveguide and its second end region to the second bus optical waveguide.

[0424] Example 13. The integrated optical circuit according to Example 12, wherein the at least one MEMS actuator includes a first electrostatic actuator configured to move the first end region of the shunt optical waveguide and a second electrostatic actuator configured to move the second end region of the shunt optical waveguide.

[0425] Example 14. An integrated optical circuit according to any of the above examples, wherein each end of the first bus optical waveguide and each end of the second bus optical waveguide includes an optical port configured to transmit light to or receive light from an external optical waveguide or external optical device.

[0426] Example 15. The integrated optical circuit according to Example 14, wherein the external optical waveguide includes an optical fiber and the optical port includes an optical fiber-to-waveguide coupler.

[0427] Example 16. The integrated optical circuit according to Example 15, wherein the fiber-to-waveguide coupler includes a surface optical coupler.

[0428] Example 17. An integrated optical circuit according to any one of Examples 1 to 16, wherein one end of the first bus optical waveguide includes an optical port and the other end of the first bus optical waveguide is optically coupled to an integrated optical device on the first waveguide layer or an integrated optical device on the second waveguide layer.

[0429] Example 18. An integrated optical circuit according to any of the examples above, wherein each end of the first bus optical waveguide includes an optical port.

[0430] Example 19. An integrated optical circuit according to any of Examples 17 and 18, further comprising one or more interlayer optical couplers configured to optically couple one or both ends of the second bus optical waveguide to one or more optical ports formed on the first waveguide layer.

[0431] Example 20. An integrated optical circuit according to any of the examples above, wherein each end of the second bus optical waveguide includes an optical port.

[0432] Example 21. An integrated optical circuit according to any of the above examples, wherein one end of the second bus optical waveguide includes an optical port and the other end of the second bus optical waveguide is optically coupled to an integrated optical device on the second waveguide layer or an integrated optical device on the first waveguide layer via an interlayer optical coupler.

[0433] Example 22. An integrated optical circuit according to any of Examples 20 and 21, further comprising one or more interlayer optical couplers configured to optically couple one or both ends of the first optical waveguide to one or more optical ports formed on the second waveguide layer.

[0434] Example 23. An integrated optical circuit according to any of Examples 17 to 22, wherein the optical port or the one or more optical ports includes an optical fiber to waveguide coupler.

[0435] Example 24. An integrated optical circuit according to any of the above examples, further comprising a first alignment structure in the first waveguide layer or on the substrate and a second alignment structure in the second waveguide layer, wherein the first alignment structure is physically or optically aligned with respect to the second alignment structure.

[0436] Example 25. The integrated optical circuit according to Example 24, wherein the first alignment structure includes a first portion of the loopback waveguide structure and the second alignment structure includes a second portion of the loopback waveguide structure.

[0437] Example 26. The integrated optical circuit according to Example 25, wherein the first portion of the loopback waveguide structure includes two optically isolated waveguide segments and the second portion of the loopback waveguide structure includes a loopback waveguide segment configured to be optically coupled to the two optically isolated waveguide segments via two interlayer optical couplers.

[0438] Example 27. An integrated optical circuit according to Example 24, wherein the first and second alignment structures include self-aligned structures of mating pairs configured to mechanically engage each other.

[0439] Example 28. The integrated optical circuit according to Example 27, wherein the self-aligning structure of the mating pair includes a pin or protrusion and a mating hole or opening.

[0440] Example 29. The integrated optical circuit according to Example 28, wherein the protrusion or pin has a hemispherical, cylindrical or rectangular shape, and the hole or opening includes a V-shaped groove, a cylindrical hole or a rectangular hole.

[0441] Example 30. An integrated optical circuit according to any of the above examples, wherein the optical alignment structure includes a pair of alignment marks each formed in one of the first or second waveguide layers.

[0442] Example VII

[0443] Example 1. A method for manufacturing an integrated optical circuit (IOC) device, the method comprising:

[0444] Manufacturing the first chip includes:

[0445] Photolithographic patterning to form a first bus optical waveguide extending within a first waveguide layer on the front side of a first substrate, and

[0446] An optical switch structure comprising a shunt optical waveguide at least partially fixedly embedded in a sacrificial material is formed on the first substrate;

[0447] Fabricating a second wafer includes photolithographically patterning to form a second optical bus waveguide extending within a second waveguide layer on the front side of a second substrate;

[0448] The front surface of the second wafer is bonded to the front surface of the first wafer;

[0449] Remove the second substrate;

[0450] Multiple vertical pathways are formed through the second waveguide layer and further through the sacrificial material, the vertical pathways acting as mechanical anchors and electrical connections between the first and second waveguide layers; and

[0451] Selectively removing the sacrificial material to release the shunt optical waveguide to configure the shunt optical waveguide to be movably optically coupled to the first bus optical waveguide and the second bus optical waveguide when activated to redirect light between the first and second bus optical waveguides.

[0452] Example 2. The method according to any of the above examples, wherein forming the optical switch structure includes forming a microelectromechanical structure and selectively removing the sacrificial material includes forming a MEMS actuator by releasing the microelectromechanical structure.

[0453] Example 3. The method according to any of the above examples, wherein bonding the second substrate to the first substrate includes aligning the first substrate relative to the second substrate such that the end portion of the shunt optical waveguide is substantially parallel to the second optical waveguide.

[0454] Example 4. The method according to any of the above examples, wherein the first substrate includes a first portion of the alignment structure, the second substrate includes a second portion of the alignment structure, and aligning the second substrate relative to the first substrate includes aligning the second portion of the alignment structure to the first portion of the alignment structure.

[0455] Example 5. According to the method of Example 4, the first portion of the alignment structure includes a pair of optically isolated waveguides and the second portion of the alignment structure includes a loopback waveguide segment configured to optically couple the pair of optically isolated waveguides when generally aligned on the first and second substrates.

[0456] Example 6. According to the method of Example 5, the alignment structure further includes an interlayer optical coupler configured to couple light between the pair of optically isolated waveguides and the loopback waveguide segment.

[0457] Example 7. The method according to Example 6, wherein the interlayer optical coupler includes a grating coupler.

[0458] Example 8. The method according to Example 6, wherein the interlayer optical coupler comprises a tapered optical waveguide.

[0459] Example 9. The method according to Example 4, wherein aligning the second substrate relative to the first substrate includes aligning the second substrate relative to the first substrate in a first direction.

[0460] Example 10. The method according to Example 9, wherein aligning the second substrate relative to the first substrate further includes aligning the second substrate relative to the first substrate in a second direction.

[0461] Example 11. The method according to Example 10, wherein the first substrate further includes a first portion of a second alignment structure, the second substrate includes a second portion of the second alignment structure, and aligning the second substrate relative to the first substrate in the second direction includes aligning the second portion of the second alignment structure to the first portion of the second alignment structure.

[0462] Example 12. The method according to Example 10, wherein the first direction is substantially perpendicular to the second direction.

[0463] Example 13. According to the method of Example 4, one of the first and second portions of the alignment structure includes a plurality of protrusions and the other includes a plurality of openings configured to receive the respective protrusions.

[0464] Example 14. The method according to Example 13, wherein bonding the second substrate to the first substrate further includes positioning the first and second substrates such that an individual protrusion of the plurality of alignment protrusions is inserted into or mechanically engaged with a corresponding individual opening of the plurality of openings.

[0465] Example 14. According to the method of Example 13, an individual protrusion of the plurality of protrusions comprises a hemisphere or column having a circular or rectangular cross-section.

[0466] Example 15. The method according to Example 13, wherein an individual protrusion of the plurality of protrusions comprises a polymeric material.

[0467] Example 16. According to the method of Example 13, an individual opening of the plurality of openings includes a V-shaped groove, an etched pyramid, or an etched cuboid.

[0468] Example 17. According to the method of Example 4, the first portion of the alignment structure includes a first plurality of openings and the second portion of the alignment structure includes a second plurality of openings.

[0469] Example 18. The method according to Example 17, wherein the first and second plurality of alignment openings include one or both of etched pyramids and V-shaped grooves.

[0470] Example 19. The method according to Example 18, wherein bonding the second substrate to the first substrate further includes providing a plurality of microbeads between the first and second substrates and positioning the first and second substrates such that individual microbeads provide mechanical connection between individual openings in the first plurality of alignment openings and corresponding individual openings in the second plurality of openings.

[0471] Example 20. The method according to any of the above examples, wherein bonding the second substrate to the first substrate includes bonding the first mechanical stop to the second mechanical stop.

[0472] Example 21. The method according to any of the above examples, wherein bonding the second substrate to the first substrate includes bonding the first bonding pad to the second bonding pad.

[0473] Example 22. The method according to Example 2, wherein selective removal of the sacrificial material includes removing the sacrificial material from the microelectromechanical structure to release the MEMS actuator.

[0474] Example Implementation VIII

[0475] Example 1. An integrated optical circuit (IOC) device, comprising:

[0476] A first waveguide layer is formed on a first substrate, and a first bus optical waveguide is formed in the first waveguide layer;

[0477] A second waveguide layer is formed on a second substrate, and a second bus optical waveguide is formed in the second waveguide layer;

[0478] An optical switch comprising a shunt optical waveguide vertically disposed in a gap between the first and second bus optical waveguide layers and configured to movably optically couple the first and second bus optical waveguides when activated to redirect light between the first and second bus optical waveguides; and

[0479] A plurality of mechanical stops extend vertically between the first and second substrates, wherein each mechanical stop has a first mechanical stop portion formed on the first substrate and a second mechanical stop portion formed on the second substrate.

[0480] The second substrate is joined to the first substrate using the mechanical stop, such that the first bus optical waveguide and the second bus optical waveguide are vertically separated by a distance defined by the mechanical stop.

[0481] Example 2. An integrated optical circuit (IOC) device according to any of the above examples, wherein the first waveguide layer includes a first buffer layer located between the first optical waveguide and the first substrate.

[0482] Example 3. An integrated optical circuit (IOC) device according to any of the above examples, wherein the second waveguide layer includes a second buffer layer located between the second bus optical waveguide and the second substrate.

[0483] Example 5. An integrated optical circuit (IOC) device according to any of the examples above, wherein the first mechanical stop portion is engaged with the second mechanical stop portion.

[0484] Example 6. An integrated optical circuit (IOC) device according to any of the above examples, wherein a first mechanical stop portion contacts a second mechanical stop portion but is not engaged with the second mechanical stop portion.

[0485] Example 7. An integrated optical circuit according to any of the examples above, wherein the first and second mechanical stop portions have a cross-sectional area greater than 10 square micrometers.

[0486] Example 8. An integrated optical circuit according to any of the examples above, wherein the shunt optical waveguide is mechanically supported by a clamping structure.

[0487] Example 9. An integrated optical circuit according to any of the above examples, wherein when the optical switch is in the ON state, more than 80% of the optical power propagating in the first optical waveguide is coupled to the second optical waveguide.

[0488] Example 10. An integrated optical circuit according to any of the examples above, wherein the optical switch further includes at least one microelectromechanical system (MEMS) actuator configured to actuate the shunt optical waveguide to optically couple its first end region to the first bus optical waveguide and its second end region to the second bus optical waveguide.

[0489] Example 11. The integrated optical circuit according to Example 10, wherein the at least one MEMS actuator includes a first electrostatic actuator configured to move the first end region of the shunt optical waveguide and a second electrostatic actuator configured to move the second end region of the shunt optical waveguide.

[0490] Example 12. An integrated optical circuit according to any of the above examples, wherein each end of the first bus optical waveguide and each end of the second bus optical waveguide includes an optical port configured to transmit light to or receive light from an external optical waveguide or external optical device.

[0491] Example 13. The integrated optical circuit according to Example 12, wherein the external optical waveguide includes an optical fiber and the optical port includes an optical fiber-to-waveguide coupler.

[0492] Example 14. The integrated optical circuit according to Example 13, wherein the fiber-to-waveguide coupler includes a surface optical coupler.

[0493] Example 15. An integrated optical circuit according to any of the above examples, wherein one end of the first bus optical waveguide includes an optical port and the other end of the first bus optical waveguide is optically coupled to an integrated optical device on the first waveguide layer or an integrated optical device on the second waveguide layer.

[0494] Example 16. An integrated optical circuit according to any of the examples above, wherein each end of the first bus optical waveguide includes an optical port.

[0495] Example 17. An integrated optical circuit according to any of Examples 17 and 18, further comprising one or more interlayer optical couplers configured to optically couple one or both ends of the second bus optical waveguide to one or more optical ports formed on the first waveguide layer.

[0496] Example 18. An integrated optical circuit according to any of the examples above, wherein each end of the second bus optical waveguide includes an optical port.

[0497] Example 19. An integrated optical circuit according to any of the above examples, wherein one end of the second bus optical waveguide includes an optical port and the other end of the second bus optical waveguide is optically coupled to an integrated optical device on the second waveguide layer or an integrated optical device on the first waveguide layer via an interlayer optical coupler.

[0498] Example 20. An integrated optical circuit according to any of Examples 18 and 19, further comprising one or more interlayer optical couplers configured to optically couple one or both ends of the first optical waveguide to one or more optical ports formed on the second waveguide layer.

[0499] Example 21. An integrated optical circuit according to any of Examples 15 to 20, wherein the optical port or the one or more optical ports includes an optical fiber to waveguide coupler.

[0500] Example 22. An integrated optical circuit according to any of the above examples, further comprising a first alignment structure in the first waveguide layer or on the substrate and a second alignment structure in the second waveguide layer, wherein the first alignment structure is physically or optically aligned with respect to the second alignment structure.

[0501] Example 23. The integrated optical circuit according to Example 22, wherein the first alignment structure includes a first portion of the loopback waveguide structure and the second alignment structure includes a second portion of the loopback waveguide structure.

[0502] Example 24. The integrated optical circuit according to Example 23, wherein the first portion of the loopback waveguide structure includes two optically isolated waveguide segments and the second portion of the loopback waveguide structure includes a loopback waveguide segment configured to be optically coupled to the two optically isolated waveguide segments via two interlayer optical couplers.

[0503] Example 25. The integrated optical circuit according to Example 22, wherein the first and second alignment structures include self-aligned structures of mating pairs configured to mechanically engage each other.

[0504] Example 26. The integrated optical circuit according to Example 25, wherein the self-alignment structure of the mating pair includes a protrusion and a mating hole or opening.

[0505] Example 27. The integrated optical circuit according to Example 26, wherein the protrusion has a hemispherical, cylindrical or rectangular shape, and the hole or opening includes a V-shaped groove, a cylindrical hole or a rectangular hole.

[0506] Example 28. An integrated optical circuit according to any of the examples above, wherein the first and second alignment structures include a pair of alignment marks each formed in one of the first or second waveguide layers.

[0507] Example 19

[0508] Example 1. A method for manufacturing an integrated optical circuit switching (OCS) device having at least one optical switching unit, the method comprising:

[0509] Manufacturing the first chip includes:

[0510] Photolithographic patterning to form a first bus optical waveguide extending within a first waveguide layer on the front side of a first substrate, and

[0511] An optical switch structure comprising a shunt optical waveguide at least partially fixedly embedded in a sacrificial material is formed on the first substrate;

[0512] Manufacturing a second chip includes:

[0513] Photolithographic patterning is used to form a second optical bus waveguide extending within a second waveguide layer on the front side of a second substrate;

[0514] Multiple mechanical stops are formed, each having a first portion formed on the first substrate and a second portion formed on the second substrate;

[0515] Selectively remove the sacrificial material to release the shunt optical waveguide; and

[0516] The second wafer is bonded to the first wafer by contacting at least the first portion of the mechanical stop with a corresponding second portion of the mechanical stop, such that the shunt optical waveguide is configured to movably optically couple the first bus optical waveguide and the second bus optical waveguide when activated to redirect light between the first and second bus optical waveguides.

[0517] Example 2. The method according to any of the above examples, wherein forming the optical switch structure includes forming a microelectromechanical system (MEMS) actuator configured to activate the shunt optical waveguide.

[0518] Example 3. The method according to any of the above examples, wherein bonding the second wafer to the first wafer includes aligning the first wafer relative to the second wafer such that the end portion of the shunt optical waveguide is substantially parallel to the second optical waveguide.

[0519] Example 4. The method according to any of the above examples, wherein the first wafer includes a first portion of the alignment structure, the second wafer includes a second portion of the alignment structure, and aligning the second wafer relative to the first wafer includes aligning the second portion of the alignment structure to the first portion of the alignment structure.

[0520] Example 5. According to the method of Example 4, the first portion of the alignment structure includes a pair of optically isolated waveguides and the second portion of the alignment structure includes a loopback waveguide segment configured to optically couple the pair of optically isolated waveguides when the first and second wafers are substantially aligned.

[0521] Example 6. According to the method of Example 5, the alignment structure further includes an interlayer optical coupler configured to couple light between the pair of optically isolated waveguides and the loopback waveguide segment.

[0522] Example 7. The method according to Example 6, wherein the interlayer optical coupler includes a grating coupler.

[0523] Example 8. The method according to Example 6, wherein the interlayer optical coupler comprises a tapered optical waveguide.

[0524] Example 9. The method according to Example 4, wherein aligning the second wafer relative to the first wafer includes aligning the second wafer relative to the first wafer in a first direction.

[0525] Example 10. The method according to Example 9, wherein aligning the second wafer relative to the first wafer further includes aligning the second wafer relative to the first wafer in a second direction.

[0526] Example 11. The method according to Example 10, wherein the first wafer further includes a first portion of a second alignment structure, the second wafer includes a second portion of the second alignment structure, and aligning the second wafer relative to the first wafer in the second direction includes aligning the second portion of the second alignment structure to the first portion of the second alignment structure.

[0527] Example 12. The method according to Example 10, wherein the first direction is substantially perpendicular to the second direction.

[0528] Example 13. According to the method of Example 4, one of the first and second portions of the alignment structure includes a plurality of protrusions and the other includes a plurality of openings configured to receive the respective protrusions.

[0529] Example 14. The method according to Example 13, wherein bonding the second wafer to the first wafer further includes positioning the first and second wafers such that individual protrusions of the plurality of alignment protrusions are inserted into or mechanically engaged with a corresponding individual opening of the plurality of ...

Claims

1. An integrated optical circuit, comprising: A first waveguide layer is formed on a substrate, and a first bus optical waveguide is formed in the first waveguide layer; The second waveguide layer, wherein a second bus optical waveguide is formed; An optical switch includes a shunt optical waveguide vertically disposed in a gap between the first and second bus optical waveguides and configured to movably optically couple the first and second bus optical waveguides when activated to redirect light between the first and second bus optical waveguides. The waveguide also includes multiple vertical channels that act as mechanical anchors and electrical connections between the first and second waveguide layers to securely suspend the second waveguide layer above the first waveguide layer. These multiple vertical channels are formed of a material selectively etched relative to the sacrificial material removed from the gap during manufacturing.

2. The integrated optical circuit of claim 1, wherein the shunt optical waveguide is configured to be optically isolated from the first and second bus optical waveguides when the optical switch is in the off state and optically coupled to the first and second bus optical waveguides when the optical switch is in the on state.

3. The integrated optical circuit according to claim 1, wherein the thickness of the second waveguide layer is less than 800 micrometers.

4. The integrated optical circuit of claim 1, wherein the optical switch further comprises at least one microelectromechanical system (MEMS) actuator configured to activate the shunt optical waveguide to optically couple a first end region to the first bus optical waveguide and a second end region to the second bus optical waveguide.

5. The integrated optical circuit of claim 1, further comprising an interlayer optical coupler configured to optically couple an end of the first bus optical waveguide to an optical port formed on the second waveguide layer or to optically couple an end of the second bus optical waveguide to an optical port formed on the first waveguide layer.

6. The integrated optical circuit of claim 5, wherein the optical port comprises a fiber-to-waveguide optical coupler.

7. The integrated optical circuit of claim 1, further comprising a first optical alignment structure in the first waveguide layer or on the substrate and a second optical alignment structure in the second waveguide layer, wherein the first optical alignment structure is configured to optically couple to the second optical alignment structure to form a loopback waveguide structure.

8. The integrated optical circuit according to claim 1, wherein one or more of the plurality of vertical paths include conductive paths.

9. The integrated optical circuit of claim 8, wherein one or more of the plurality of vertical paths comprises a dielectric region.

10. A method for manufacturing an integrated optical circuit device, the method comprising: Fabricating a first wafer includes: photolithographically patterning a first bus optical waveguide extending within a first waveguide layer on a front side of a first substrate; and forming an optical switch structure on the first substrate including a shunt optical waveguide at least partially fixedly embedded in a sacrificial material; fabricating a second wafer includes photolithographically patterning a second bus optical waveguide extending within a second waveguide layer on a front side of a second substrate; bonding the front side of the second wafer to the front side of the first wafer; removing the second substrate; forming a plurality of vertical pathways through the second waveguide layer and further through the sacrificial material, the plurality of vertical pathways acting as mechanical anchors and electrical connections between the first and second waveguide layers; and selectively removing the sacrificial material to release the shunt optical waveguide to configure the shunt optical waveguide to movably optically couple the first bus optical waveguide and the second bus optical waveguide when activated to redirect light between the first and second bus optical waveguides.

11. The method of claim 10, wherein forming the optical switch structure includes forming a microelectromechanical system (MEMS) structure.

12. The method of claim 11, wherein selective removal of the sacrificial material comprises removing the sacrificial material from the MEMS structure to release a MEMS actuator configured to activate the shunt optical waveguide.

13. The method of claim 12, wherein the sacrificial material comprises a material selectively etched relative to the MEMS actuator and the shunt optical waveguide.

14. The method of claim 10, wherein bonding the second wafer to the first wafer includes optically aligning the shunt optical waveguide and the second bus optical waveguide such that, after the sacrificial material is removed, the shunt optical waveguide is movably optically coupled to the first bus optical waveguide and the second bus optical waveguide when activated.

15. The method of claim 10, wherein bonding the second wafer to the first wafer includes optically coupling a pair of optical isolation waveguides formed on the first wafer and a loopback waveguide segment formed on the second wafer.

16. The method of claim 10, wherein forming the plurality of vertical pathways comprises forming conductive lines extending vertically from the first wafer to the second wafer.

17. An integrated optical circuit device, comprising: A first waveguide layer is formed on a first substrate, and a first bus optical waveguide is formed in the first waveguide layer; A second waveguide layer is formed on a second substrate, and a second bus optical waveguide is formed in the second waveguide layer; An optical switch includes a shunt optical waveguide disposed in a vertical gap between the first and second bus optical waveguide layers and configured to movably optically couple the first and second bus optical waveguides when activated to redirect light between the first and second bus optical waveguides. and a plurality of mechanical stops extending vertically between the first and second substrates, wherein each mechanical stop has a first mechanical stop portion formed on the first substrate and a second mechanical stop portion formed on the second substrate, wherein the second substrate is joined to the first substrate using the plurality of mechanical stops such that the first bus optical waveguide and the second bus optical waveguide are vertically separated by a distance defined by the mechanical stops.

18. The integrated optical circuit device of claim 17, wherein the plurality of mechanical stops are configured to establish a predefined vertical spacing between the first and second bus optical waveguides.

19. The integrated optical circuit device of claim 17, wherein the first mechanical stop portion is engaged with the second mechanical stop portion.

20. The integrated optical circuit device of claim 17, further comprising a first optical alignment structure located in the first waveguide layer or on the first substrate and a second optical alignment structure located in the second waveguide layer or on the second substrate, the first optical alignment structure being configured to optically couple to the second optical alignment structure to form a loopback waveguide structure.

21. The integrated optical circuit device of claim 20, wherein the optical switch is formed over a first region of the first substrate and the first optical alignment structure is formed in a second region of the first substrate, and wherein the first and second regions do not overlap.

22. The integrated optical circuit device of claim 17, wherein the optical switch further comprises at least one microelectromechanical system (MEMS) actuator configured to activate the shunt optical waveguide to optically couple a first end region to the first bus optical waveguide and a second end region to the second bus optical waveguide.

23. The integrated optical circuit device of claim 17, wherein the shunt optical waveguide is mechanically connected to the first substrate via a clamping structure.

24. A method for manufacturing an integrated optical circuit switching device having at least one optical switching unit, the method comprising: Fabricating a first wafer includes: photolithographically patterning a first bus optical waveguide extending within a first waveguide layer on a front side of a first substrate; and forming an optical switch structure on the first substrate including a shunt optical waveguide at least partially fixedly buried in a sacrificial material; fabricating a second wafer includes: photolithographically patterning a second bus optical waveguide extending within a second waveguide layer on a front side of a second substrate; forming a plurality of mechanical stops, each having a first portion formed on the first substrate and a second portion formed on the second substrate; selectively removing the sacrificial material to release the shunt optical waveguide; and bonding the second wafer to the first wafer by contacting at least the first portion of the mechanical stops with a corresponding second portion of the mechanical stops, such that the shunt optical waveguide is configured to movably optically couple the first bus optical waveguide and the second bus optical waveguide when activated to redirect light between the first and second bus optical waveguides.

25. The method of claim 24, wherein forming the optical switch structure includes forming a microelectromechanical structure.

26. The method of claim 25, wherein selective removal of the sacrificial material comprises removing the sacrificial material from the microelectromechanical structure to release a MEMS actuator configured to activate the shunt optical waveguide.

27. The method of claim 26, wherein the MEMS actuator includes a lever beam configured to optically couple the end of the shunt optical waveguide to the second bus optical waveguide.

28. The method of claim 24, wherein bonding the second wafer to the first wafer includes optically aligning the shunt optical waveguide and the second bus optical waveguide such that, after the sacrificial material is removed, the shunt optical waveguide is movably optically coupled to the first bus optical waveguide and the second bus optical waveguide when activated.

29. The method of claim 28, wherein optical alignment of the shunt optical waveguide and the second bus optical waveguide includes optically coupling the first optical alignment structure to the second optical alignment structure based on measured optical power transfer from a first portion to a second portion of the first optical alignment structure formed on the first wafer via a second optical alignment structure formed on the second wafer.

30. The method of claim 24, wherein bonding the second wafer to the first wafer includes engaging the first and second portions of the mechanical stop.

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