Polarization-diversity integrated photonic switch with multilayer waveguides

Abstract

A photonic integrated circuit (PIC) is provided, including a polarization-diversity silicon photonic switch having a multilayer waveguide. The PIC of this disclosure can be applied to or used in a wide variety of fields, including but not limited to optical fiber communications, photonic computing, and light detection and ranging (LiDAR). The proposed PIC may include a switch having two polarization-decomposing channels propagating in a closely spaced dual-channel waveguide, achieving polarization-diversity operation without increasing the PIC area. The proposed scheme also eliminates waveguide crossings found in the prior art by coupling light from one layer to the other using a two-layer waveguide and a dual-channel micro-electromechanical system (MEMS) actuated switching element.

Description

Technical Field

[0001] Claim of Priority

[0001] This patent application claims the priority of U.S. Provisional Patent Application No. 63 / 488,741, filed on Mar. 6, 2023, entitled "POLARIZATION-DIVERSE INTEGRATED PHOTONIC SWITCH WITH MULTI-LAYER WAVEGUIDES", the entire content of which is incorporated herein by reference.

[0002]

[0002] The present disclosure relates to optical communication networks. More particularly, the present disclosure details a novel polarization-diverse integrated photonic switch with low polarization-dependent loss, low different group delay, and low on-chip loss. Statement Regarding Federally Sponsored Research

[0003] This invention was made with government support under Contract / Award No. HR0011-19-2-0015 awarded by the Defense Advanced Research Projects Agency (DARPA) and Contract / Award No. DE-AR0000849 awarded by the Advanced Research Projects Agency-Energy (ARPA-E). The U.S. government has certain rights in this invention.

Background Art

[0003]

[0004] The emergence of data-intensive cloud computing, high-performance computing (HPC), artificial intelligence (AI), and machine learning (ML) systems has led to an explosive increase in data traffic in data center networks. Traditional electric packet switches supporting optical networks within current data centers face the challenge of increasing energy consumption as the required data rate—the speed at which data is transmitted—continues to rise. Optical circuit switches can address these challenges by providing unlimited bandwidth thanks to their low power consumption, which is independent of the data rate.

[0004]

[0005] Silicon photonics, leveraging advanced CMOS foundry manufacturing, is a practical technology platform for demonstrating large-scale optical switches. Silicon photonic devices typically utilize waveguides formed in thin silicon-on-insulator (SOI) layers, with countless photonic components routed through these waveguides to provide complex functions. Integrated optical switches implemented on a silicon photonics platform, so-called silicon photonic switches, offer high-density integration and low-cost manufacturing. However, their operation is typically limited to fixed optical polarization (TE or TM) due to the birefringence of the rectangular waveguide.

[0005]

[0006] To address this polarization problem, polarization-diversity silicon photonic devices have been proposed, in which propagating light of any polarization is decomposed into two optical channels with the same preferred polarization by a polarization processing photonic component such as a polarization splitter rotator (PSR). Each of the divided channels is sent to a duplicated photonic integrated circuit (PIC), through which it passes, and finally the two channels are recoupled into a single waveguide by another polarization component such as a polarization splitter rotator (PSR). Therefore, polarization-diversity silicon photonic devices typically require twice the area because the PICs are duplicated. Furthermore, countless waveguide crossings are required to route the two polarization-decomposed channels of each I / O port to the duplicated PICs, resulting in excessive waveguide crossing losses. These requirements limit the scalability of polarization-diversity silicon photonic switches.

[0006]

[0007] U.S. Patent No. 10,715,588 describes a polarization-independent silicon photonic switch system comprising an array of horizontal waveguides in one layer and an array of vertical waveguides in another layer. These layers are physically separated sufficiently so as not to optically interact with each other. A vertically moving coupler transmits light between the waveguides of the two different layers. The thermal insulation of the moving coupler allows for the coupling of both polarizations (TE and TM). One drawback of such a polarization-independent system is that light of both polarizations propagates simultaneously within a single waveguide, and the birefringence of the waveguide creates a group delay difference, resulting in an increased bit error rate (BER). [Overview of the project] [Problems that the invention aims to solve]

[0007] [Means for solving the problem]

[0008]

[0008] A substrate; one or more rows of horizontal waveguides arranged on a first layer of the substrate, wherein each row of horizontal waveguides includes a first horizontal waveguide and a second horizontal waveguide; one or more columns of vertical waveguides arranged on a second layer of the substrate, wherein each column of vertical waveguides includes a first vertical waveguide and a second vertical waveguide; one or more input polarization-independent couplers configured to couple external light to one or more rows of horizontal waveguides; and input polarization splitter rotors (PSR) coupled to each of the one or more input polarization-independent couplers. A photonic integrated circuit (PIC) device is provided, comprising: an input polarization splitter rotor (PSR) configured such that each input PSR splits coupled light into a first horizontal waveguide and a second horizontal waveguide of one or more rows of horizontal waveguides; and a matrix of polarization diversity photonic switches positioned at the intersection of one or more rows of horizontal waveguides and one or more rows of vertical waveguides, which are operable to transfer light from the first and second horizontal waveguides of a given row of horizontal waveguides to the first and second vertical waveguides of the vertical waveguides of the intersecting columns.

[0009]

[0009] In some embodiments, the PIC further comprises output PSRs coupled to each of one or more rows of vertical waveguides, each output PSR configured to couple light from the first and second vertical waveguides to a single output waveguide.

[0010]

[0010] In some embodiments, the PIC further comprises one or more output polarization-independent couplers coupled to each output waveguide.

[0011] In some embodiments, the input PSR is configured to split the input light into two orthogonal polarizations in two separate waveguides, and to rotate the polarization of one of the two separate waveguides to achieve the same polarization in the two separate waveguides.

[0011]

[0012] In other embodiments, polarization-diversity photonic switches are micro-electromechanical system (MEMS) switches.

[0013] In one embodiment, the polarization diversity photonic switch comprises first and second waveguide couplers disposed on a third layer of a substrate.

[0012]

[0014] In some embodiments, the third layer is located on top of the first and second layers.

[0015] In another embodiment, the third layer lies between the first and second layers.

[0016] In some embodiments, the first and second waveguide couplers are configured to be actuated by a MEMS to contact the first and second horizontal waveguides.

[0013]

[0017] In one embodiment, the first and second waveguide couplers are configured to be actuated by a MEMS to contact the first and second vertical waveguides.

[0018] In other embodiments, the first and second horizontal waveguides are configured to be actuated by a MEMS to contact the first and second waveguide couplers.

[0014]

[0019] In some embodiments, the first and second vertical waveguides are configured to be actuated by a MEMS to contact the first and second waveguide couplers.

[0020] In other embodiments, the polarization diversity photonic switch comprises overlapping sections of first and second horizontal waveguides and overlapping sections of first and second vertical waveguides.

[0015]

[0021] In some embodiments, the overlapping sections include several bends or curves in both the horizontal and vertical waveguides, thereby enabling alignment between the overlapping portions of the horizontal and vertical waveguides.

[0016]

[0022] In one embodiment, the overlapping portion of the horizontal waveguide is parallel to the overlapping portion of the vertical waveguide.

[0023] In other embodiments, the input and output terminals of the horizontal waveguide are orthogonal to the input and output terminals of the vertical waveguide.

[0017]

[0024] A substrate; one or more rows of horizontal waveguides arranged on a first layer of the substrate, each row of horizontal waveguides including a transmit port, a receive port, a first horizontal waveguide, and a second horizontal waveguide; one or more columns of vertical waveguides arranged on a second layer of the substrate, each column of vertical waveguides including a transmit port, a receive port, a first vertical waveguide, and a second vertical waveguide; and a transmit polarization splitter rotor (PSR) coupled to each of the transmit ports of the horizontal waveguides and each of the transmit ports of the vertical waveguides, wherein each transmit PSR splits the light into the first horizontal waveguide and the second horizontal waveguide of each of the one or more rows of horizontal waveguides, and the one or more rows of vertical waveguides A photonic integrated circuit (PIC) device is provided, comprising: a transmit polarization splitter rotor (PSR) configured to split each of the waveguides into a first vertical waveguide and a second vertical waveguide; and a matrix of polarization diversity photonic switches positioned at the intersections of one or more rows of horizontal waveguides and one or more rows of vertical waveguides, wherein the polarization diversity photonic switches are operable to transfer light from the first and second horizontal waveguides corresponding to a given transmit port to the first and second vertical waveguides corresponding to a pair of receive ports, and to transfer light from the first and second vertical waveguides corresponding to a given transmit port to the first and second horizontal waveguides corresponding to a pair of receive ports.

[0018]

[0025] In some embodiments, the PIC further comprises a receiving PSR coupled to each of the receiving ports of the horizontal waveguide and each of the receiving ports of the vertical waveguide, each receiving PSR configured to couple light from the first and second vertical waveguides or the first and second horizontal waveguides to a single output waveguide.

[0019]

[0026] In another embodiment, the transmitting PSR is configured to split light into two orthogonal polarizations in two separate waveguides and rotate the polarization of one of the two separate waveguides to achieve the same polarization in the two separate waveguides.

[0020]

[0027] In some embodiments, polarization-diversity photonic switches are micro-electromechanical system (MEMS) switches.

[0028] In other embodiments, the polarization diversity photonic switch comprises first and second waveguide couplers disposed on a third layer of a substrate, the first and second waveguide couplers configured to couple the transmit port of a horizontal waveguide in a given row to the receive port of a vertical waveguide in a corresponding column.

[0021]

[0029] In one embodiment, the polarization diversity photonic switch comprises third and fourth waveguide couplers disposed on a third layer of a substrate, the first and second waveguide couplers configured to couple the transmit ports of vertical waveguides in a given row to the receive ports of horizontal waveguides in the corresponding row.

[0022]

[0030] In some embodiments, the third layer is located on top of the first and second layers.

[0031] In a further embodiment, the third layer lies between the first and second layers.

[0032] In some embodiments, the first and second waveguide couplers are configured to be actuated by a MEMS to contact the first and second horizontal waveguides.

[0023]

[0033] In other embodiments, the first and second waveguide couplers are configured to be actuated by a MEMS to contact the first and second vertical waveguides.

[0034] In some embodiments, the first and second horizontal waveguides are configured to be actuated by a MEMS to contact the first and second waveguide couplers.

[0024]

[0035] In one embodiment, the first and second vertical waveguides are configured to be actuated by a MEMS to contact the first and second waveguide couplers.

[0036] In other embodiments, the polarization diversity photonic switch comprises overlapping sections of first and second horizontal waveguides and overlapping sections of first and second vertical waveguides.

[0025]

[0037] In one embodiment, the overlapping sections include several bends or curves in both the horizontal and vertical waveguides, thereby enabling alignment between the overlapping portions of the horizontal and vertical waveguides.

[0026]

[0038] In other embodiments, the overlapping portion of the horizontal waveguides is parallel to the overlapping portion of the vertical waveguides.

[0039] In one embodiment, the input and output terminals of the horizontal waveguide are orthogonal to the input and output terminals of the vertical waveguide.

[0027]

[0040] A method is provided for guiding light through a photonic integrated circuit (PIC), the method comprising the steps of: inputting light into a row of horizontal waveguides on a first layer of the PIC; splitting the light into a first horizontal waveguide and a second horizontal waveguide of the horizontal waveguide in this row; controlling an array of micro-electromechanical systems (MEMS) photonic switches to transfer light from the first and second horizontal waveguides to first and second vertical waveguides of a vertical waveguide in a selected row; and outputting light from the vertical waveguide in the selected row.

[0028]

[0041] In some embodiments, the method further includes the step of coupling light from first and second vertical waveguides into a single output before outputting light.

[0042] In another embodiment, the method further includes the steps of splitting light into first and second horizontal waveguides with two orthogonal polarizations, and then rotating the polarization of one of the first and second horizontal waveguides to achieve the same polarization in the first and second horizontal waveguides.

[0029]

[0043] Novel features of the present invention are described in detail in the following claims. A better understanding of the features and advantages of the present invention will be obtained by referring to the following detailed description and accompanying drawings which describe exemplary embodiments in which the principles of the present invention are utilized. [Brief explanation of the drawing]

[0030] [Figure 1A]

[0044] This figure shows the OFF state of a polarization-independent switch where the input waveguide and output waveguide are in separate layers. The switching element may include a MEMS-operated adiabatic coupler. [Figure 1B] This figure shows the ON state of a polarization-independent switch where the input waveguide and output waveguide are in separate layers. The switching element may include a MEMS-operated adiabatic coupler. [Figure 2A]

[0045] This figure shows the OFF state of a dual-channel polarization diversity switch where the input waveguide and output waveguide are in separate layers. Orthogonal polarization components (TE and TM) are coupled to different channels in the paired waveguides by a polarization splitter rotor (PSR). The dual-channel MEMS switching element couples both channels from one layer to the other. After switching, the polarization components are coupled by another PSR. [Figure 2B] This diagram shows the ON state of a dual-channel polarization diversity switch where the input and output waveguides are in separate layers. Orthogonal polarization components (TE and TM) are coupled to different channels in the paired waveguides by a polarization splitter rotor (PSR). The dual-channel MEMS switching element couples both channels from one layer to the other. After switching, the polarization components are coupled by another PSR. [Figure 3A]

[0046] This figure shows one embodiment of a dual-channel switching element. The figure shows that the MEMS-operated dual-channel coupler is located in a third layer above the input waveguide and output waveguide. [Figure 3B] This figure shows one embodiment of a dual-channel switching element. The figure shows that the MEMS-operated dual-channel coupler is located in a third layer above the input waveguide and output waveguide. [Figure 3C] This figure shows one embodiment of a dual-channel switching element. It also shows a MEMS-operated dual-channel coupler sandwiched between the input waveguide and the output waveguide. [Figure 3D] This figure shows one embodiment of a dual-channel switching element. It also shows a MEMS-operated dual-channel coupler sandwiched between the input waveguide and the output waveguide. [Figure 3E] This figure shows one embodiment of a dual-channel switching element. The figure shows a switching element including the overlapping portion of the input waveguide and the output waveguide. One or both waveguides are connected to a MEMS actuator. [Figure 3F] This figure shows one embodiment of a dual-channel switching element. The figure shows a switching element including the overlapping portion of the input waveguide and the output waveguide. One or both waveguides are connected to a MEMS actuator. [Figure 4]

[0047] This diagram shows a polarization-diversified dual switch that enables simultaneous transmit / receive (T / R) operation. [Figure 5A]

[0048] This figure shows one embodiment of a polarization-diversified dual switching element. [Figure 5B] This figure shows one embodiment of a polarization-diversified dual switching element. [Figure 5C] This figure shows one embodiment of a polarization-diversified dual switching element. [Figure 5D] This figure shows one embodiment of a polarization-diversified dual switching element. [Figure 6]

[0049] This figure shows an embodiment of a polarization-independent dual switch. [Figure 7]

[0050] This figure shows another embodiment of a polarization diversity switch that does not use a dual-channel waveguide or switching element. [Figure 8]

[0051] This figure shows one embodiment of a polarizing splitter rotor (PSR). [Figure 9]

[0052] Figure 9A shows another embodiment of the dual-channel switching element. It is a 3D rendering of the switching element. Figure 9B shows another embodiment of the dual-channel switching element. It is a simulated mode profile along a deformable waveguide coupler. [Figure 10]

[0053] This figure shows a 3D rendering of one embodiment of a dual-channel switching element. [Modes for carrying out the invention]

[0031]

[0054] This disclosure details a novel photonic integrated circuit (PIC) including a polarization-diversity silicon photonic switch having a multilayer waveguide. Generally, the PICs of this disclosure are configured to detect, generate, transport, and / or process light. The PICs of this disclosure can be applied to or used in a wide variety of fields, including but not limited to optical fiber communications, photonic computing, and light detection and ranging (LiDAR). The proposed PIC may include a switch having two polarization-decomposing channels propagating in a closely spaced dual-channel waveguide, achieving polarization-diversity operation without increasing the PIC area. The proposed scheme also eliminates waveguide crossings found in the prior art by coupling light from one layer to the other using a two-layer waveguide and a dual-channel micro-electromechanical system (MEMS) actuated switching element.

[0032]

[0055] Figures 1A to 1B respectively show the OFF state and the ON state of the PIC100 including the matrix 101 of polarization-independent photonic switches 102 arranged on the substrate 104. The PIC can further include an array of horizontal waveguides 106 and another array of vertical waveguides 107 used together with the photonic switches 102 arranged at intersections. The array of horizontal waveguides is coupled to polarization-independent input / output (I / O) couplers 108 on both sides of the waveguide, and defines ports of rows A1 to A N and the array of vertical waveguides is coupled to polarization-independent I / O couplers 108 on both sides of the waveguide, and defines ports of columns B1 to B M .

[0033]

[0056] For ease of illustration and description, the photonic switches are labeled according to the intersecting rows and columns. Thus, the optical switch present at the intersection of row A1 and column B1 is labeled as optical switch 102 1、1 and the optical switch present at the intersection of row A1 and column B M is labeled as optical switch 102 1、M . Similarly, the optical switch present at the intersection of row A N and column B1 is labeled as optical switch 102 N、1 and the optical switch present at the intersection of row A N and column B M is labeled as optical switch 102 N、M . Similar labeling is used for the horizontal waveguides, vertical waveguides, and I / O couplers. Thus, the horizontal waveguides of rows A1 to A N are labeled as horizontal waveguides 1061 to 106 N and the vertical waveguides of columns B1 to B M are labeled as vertical waveguides 1071 to 107 M . The I / O couplers 108 are defined according to the side of the PIC they are on, in combination with the row or column number. Thus, the I / O couplers on the west side of the PIC span (with respect to the page) are couplers 108 W、1 to 108 W、NLabeled as such, the I / O coupler on the north side of the PIC span is coupler 108. N、1 ~108 N、M Labeled as such, the I / O coupler on the east side of the PIC span is coupler 108. E、1 ~108 E、N Labeled as such, the I / O coupler on the south side of the PIC span is coupler 108. S、1 ~108 S、M It is labeled as such. Not all elements are labeled in all figures, but this labeling method will be obvious to those skilled in the art.

[0034]

[0057] To demonstrate switching operation at arbitrary polarizations, polarization-independent operation is required for all photonic components of the switch, such as I / O couplers, waveguide crossovers, and photonic switches. This requirement is difficult to achieve with conventional silicon photonic switches based on thermo-optic (TO) / electro-optic (EO) Mach-Zehnder interferometers (MZI) or microring resonators (MRRs), because rectangular waveguides are inherently birefringent, and the optimal conditions for optical coupling between single-layer, transversely arranged waveguides differ depending on the polarization.

[0035]

[0058] In the embodiment of Figure 1A, all photonic switches 102 are in the OFF position, which means that light passes through the horizontal waveguide 106 and / or vertical waveguide 107 without being switched to a different waveguide or layer. For example, light passing through the horizontal waveguide 1061 remains in that waveguide, and light passing through the vertical waveguide 1071 remains in that waveguide. However, in the embodiment of Figure 1B, the photonic switches 102 1、M-1 , 102 2、1 , 102 3、2 , 102 N-1、M , and 102 N、3 The switch is turned to the ON position, thereby allowing light passing through the horizontal waveguide 1061 to switch 102 1、M-1 by vertical waveguide 107 M-1 It can be switched to this. The light path through the other ON switches is also shown in the diagram.

[0036]

[0059] Figures 2A and 2B show schematic diagrams of the PIC200 including the matrix of polarization-diversity silicon photonic switches 202. In Figure 2A, the photonic switches are shown in the OFF state, and in Figure 2B, a portion of the switches are shown in the ON state. As shown, the PIC has horizontal waveguides 2061-206 on one layer of the substrate. N The array includes vertical waveguides 2071-207 in another layer of the substrate. M This can include an array of waveguides. For example, different layers of waveguides can be integrated into different layers on the PIC substrate through a wafer manufacturing process. Light is polarity-independent coupler 208 (e.g., West coupler 208) W、1 ~208 W、N East Coupler 208 E、1 ~208 E、N North Kapra 208 N、1 ~208 N、M , and South Coupler 208 S、1 ~208 S、M Coupled to the waveguide from an external fiber or free-space beam via ). One or more polarization splitter rotors (PSRs) 210 in each row / column (e.g., West PSR210) W、1 ~210 W、N , East PSR210 E、1 ~210 E、N , North PSR210 N、1 ~210 N、M , and South PSR210 S、1 ~210 S、M ) is configured to split the coupled light into two orthogonal polarizations in two separate waveguides (for example, horizontal waveguide 2061 is connected to two waveguides 206 1、1 and 206 1、2 It is divided into horizontal waveguide 206 N This involves two waveguides 206 N、1 and 206 N、2 It is divided into two waveguides 207 1、1 and 207 1、2 It is divided into vertical waveguide 207 M This is two waveguides 207 M、1 and 207 M、2(The light is split into two waveguides), and the polarization of one waveguide is rotated to match the polarization of the other waveguide. In other words, the coupled light is split into pairs of waveguides in each row / column and rotated so that the polarization of both pairs of waveguides becomes the same. Because the two waveguides have the same dimensions and shape, and the light in them has the same polarization, the photonic switch along the waveguide is not affected by the group delay difference.

[0037]

[0060] Referring to Figure 2B, the split light in two parallel waveguides propagates until it reaches an ON-state optical switch. In the ON-state switch cell, the light in the two parallel waveguides is transferred by a pair of waveguide couplers to another pair of waveguides in a second layer. The transferred pair of light in the second-layer waveguides propagates to another PSR and is coupled into a single waveguide. The coupled light is finally coupled to an external fiber or free-space beam via a polarization-independent coupler. In one specific example in Figure 2B, the coupled light in row A1 is coupled to polarization-independent coupler 208 W、1 PSR210 passes through waveguide 2061 W、1 It propagates to the waveguide 206, and this PSR splits and rotates the light, which has the same polarization. 1、1 and 206 1、2 It leads to the light switch 202 in the ON state. 1、M-1 These waveguides are followed until they reach optical switch 202 1、M-1 This is the waveguide 206 of the first layer of the substrate. 1、1 and 206 1、2 waveguide 207 of the second layer of the substrate 1、1 and 207 1、2 Light is transferred to the PSR210. S、M-1 It propagates through these waveguides and PSR210 S、M-1 The light is coupled into waveguide 207 M-1 Return to the polarization-independent coupler 208 S、M-1 The output is coupled to an external fiber or free space via this. Other photonic switches in the matrix shown in Figure 2B are also shown in the ON state, indicating the transfer of light between the rows and columns of the PIC waveguide, as described above.

[0038]

[0061] Figures 3A and 3B show top and perspective views of embodiments of a photonic switch or switch cell 302a. As described above, the switch cell 302a may include a MEMS switch containing a MEMS element that can be actuated to control the operation of the switch cell. A pair of horizontal waveguides 3061 and 3062 are mounted as the first layer from the substrate (not shown). A pair of vertical waveguides 3071 and 3072 are mounted as the second layer from the substrate. A pair of waveguide couplers 3121 and 3122 are mounted as the third layer from the substrate. If the first, second, and third layers of the substrate are considered to be vertical layers on the substrate, the first layer may constitute the bottom layer, the second layer may constitute the intermediate layer, and the third layer may constitute the top layer. In the OFF state, the waveguide couplers are located away from the horizontal and vertical waveguides. In the ON state, the first ends 3141 and 3142 of the paired waveguide coupler are actuated by the MEMS to pull them down to the horizontal waveguide pair of the first layer, achieving optical coupling between the horizontal waveguides 3061 and 3062 and the waveguide coupler. The second ends 3143 and 3144 of the paired waveguide coupler are actuated by the MEMS to pull them down to the vertical waveguide of the second layer, achieving optical coupling between the waveguide coupler and the vertical waveguide. In another embodiment, instead of acting the waveguide coupler by the MEMS, the horizontal waveguide and / or vertical waveguide can be actuated by the MEMS to pull them up toward the coupler waveguide, thereby achieving optical coupling while keeping the coupler waveguide at the same level. In another embodiment, both the horizontal / vertical waveguide and the coupler waveguide are pulled toward each other and contact at an intermediate level. In any of the embodiments described herein, the width of the waveguide and / or waveguide coupler can be varied in thickness or width. Furthermore, waveguides and / or waveguide couplers can be tapered.

[0039]

[0062] Figures 3C to 3D show top and perspective views of another embodiment of the photonic switch or switch cell 302b. In this embodiment, waveguide couplers 3121 and 3122 are mounted in an intermediate or second layer of the substrate between the layers of horizontal waveguides 3061 and 3062 and the layers of vertical waveguides 3071 and 3072. In the OFF state, the waveguide couplers are separated from the horizontal and vertical waveguides so as not to interact optically. In the ON state, optical coupling can be achieved by operating the waveguide couplers with a MEMS to move them toward the horizontal and vertical waveguides. For example, since the waveguide couplers are in the intermediate layer in this embodiment, this embodiment may include a MEMS that operates to pull down the first ends 3141 and 3142 of the waveguide couplers toward the horizontal waveguides, and a MEMS that operates to pull up the second ends 3143 and 3144 toward the vertical waveguides. Alternatively, a combination of MEMS that operates waveguide couplers, horizontal waveguides, and / or vertical waveguides can be implemented, which may include moving the horizontal / vertical waveguides toward the waveguide couplers, or moving both the horizontal / vertical waveguides and the waveguide couplers toward each other simultaneously.

[0040]

[0063] Figures 3E to 3F show top and perspective views of another embodiment of the photonic switch or switch cell 302c. In this embodiment, optical coupling is achieved not by a waveguide coupler in a separate layer, but by an overlapping section 316 of horizontal waveguides 3061 and 3062 and vertical waveguides 3071 and 3072 arranged in the first and second layers of the substrate. As shown in Figures 3E to 3F, in the overlapping section 316, each of the horizontal and vertical waveguides may include several bends or curves 318, which allows for alignment or coincidence of the overlapping portion of the horizontal waveguide in the overlapping section 316 with the corresponding overlapping portion of the vertical waveguide in the overlapping section. The input and output ends of the horizontal waveguide remain parallel to each other, as do the input and output ends of the vertical waveguide. However, the bends or turns in each waveguide allow for alignment of the overlapping portions of the vertical waveguide and the horizontal waveguide. In one example, the bends or turns may include 45-degree bends or turns, which facilitates the overlap of the vertical and horizontal waveguides while still allowing the horizontal waveguide to be roughly perpendicular to the vertical waveguide. To elaborate further, the overlapping portion of the horizontal waveguide is aligned with and parallel to the overlapping portion of the vertical waveguide, while the input and output ends of the horizontal waveguide are perpendicular to the input and output ends of the vertical waveguide.

[0041]

[0064] In the OFF state, the two layers of waveguides 306a / c and 306b / d are sufficiently spaced apart from each other so as not to interact optically. In the ON state, light is coupled by the MEMS acting the horizontal and / or vertical waveguides toward each other. The width of the waveguides in the overlapping sections can remain constant, like a conventional directional coupler, or it can be tapered, like an adiabatic coupler.

[0042]

[0065] The proposed polarization diversity switch is bidirectional due to the reciprocal nature of light propagation in a linear isotropic medium. However, optical network nodes typically have separate transmit (Tx) and receive (Rx) ports, which necessitates an optical circulator at each port of the bidirectional switch, or the switch being duplicated for the Tx and Rx channels. Figure 4 shows an embodiment of the PIC 400 on a substrate 404 including an array or matrix of polarization diversity Tx / Rx duplicated switches 402 without implementing optical circulators or switch duplication. The PIC may include the aforementioned components, including a coupler 408, a PSR 410, and vertical and horizontal waveguides, as shown. In the proposed PIC, the western and eastern end ports of the horizontal waveguide are paired (e.g., coupler 408) W、1 and 408 E、1 ) is the Tx / Rx pair of the switch port (A1, A2, ..., A N ) forms. Similarly, the pair of north and south end ports of the vertical waveguide (e.g., coupler 408) N、M-1 and 408 S、M-1 ) is a Tx / Rx pair for another switch port (B1, B2, ..., B M ) is formed. When switch cell (n, m) is turned on, the Tx port and Rx port of the corresponding cell are connected simultaneously (A n -Tx and B m -Rx, A n -Rx and B m -Tx). For example, switch 402 1、M-1 When it is turned on, coupler 408 W、1 and 408 S、M-1 These form a Tx / Rx pair, and coupler 408 N、M-1 and 408 E、1 These form a Tx / Rx pair.

[0043]

[0066] Figures 5A to 5D show embodiments of a photonic switch or redundant switch cell 502a / 502b having a three-layer waveguide consisting of a horizontal waveguide, a vertical waveguide, and waveguide couplers. The operating principle of these is similar to the previous embodiments without Tx / Rx redundancy shown in Figures 3A to 3D. The only difference is that the redundant switch has an additional pair of waveguide couplers 5123 and 5124 to achieve optical coupling not only between the west port and the south port, but also between the north port and the east port. For example, in Figures 5A to 5B, waveguide couplers 5121 and 5122 couple the west ports of the horizontal waveguides 5061 and 5062 to the south ports of the vertical waveguides 5071 and 5072. Furthermore, waveguide couplers 5123 and 5124 couple the north ports of the vertical waveguides 5071 and 5072 to the east ports of the horizontal waveguides 5061 and 5062. As described above, optical connection can be made by operating any combination of waveguides or waveguide couplers using MEMS. In Figures 5A to 5B, the horizontal waveguide is on the first (bottom) layer of the substrate, the vertical waveguide is on the second (middle) layer of the substrate, and the waveguide coupler is on the third (top) layer of the substrate. However, in the embodiments of Figures 5C to 5D, the switch 502b is designed to have a waveguide coupler on the second (middle) layer and a vertical waveguide on the third (top) layer. As described above, optical connection can be made between the waveguide and the coupler by operating the waveguide coupler and / or the waveguide itself using MEMS.

[0044]

[0067] In another embodiment, similar to the embodiment shown in FIGS. 3E - 3F, the Tx / Rx duplex switch can be demonstrated without using a separate layer for the waveguide coupler. In the proposed duplex switch, since the single - port Tx and Rx pairs are connected by waveguides, crosstalk may occur between the Tx port and the Rx port. In some embodiments, a movable optical attenuator can be used to reduce the channel crosstalk between the Tx port and the Rx port in the ON state. Similarly, an array of polarization - independent duplex switches 602 can also be demonstrated as shown in FIG. 6. In this example, a single waveguide is used for the horizontal waveguides of each row and the vertical waveguides of each column. The polarization - independent multiplexing switch 602 1、M-1 couples the A1Tx port to the B M-1 Rx port and at the same time, couples the B M-1 Tx port to the A1Rx port.

[0045]

[0068] The polarization diversity switch (FIGS. 2A - 2B) previously proposed in this disclosure uses a dual - channel waveguide in the switch cell to deliver two split polarizations. FIG. 7 shows a potential embodiment of a polarization diversity switch without waveguide duplication in the switch cell. In the proposed architecture, the light coupled by the coupler 708 W、2 is split for each polarization by the PSR710 W、2 and supplied to both ends (the west end and the east end) of the horizontal waveguide or both ends (the north end and the south end) of the vertical waveguide. The switch cell 702 2、1 forms optical connections between the west port and the north port and between the east port and the south port in the ON state.

[0046]

[0069] FIG. 8 shows an embodiment of a polarization splitter rotator (PSR) 810 that can include an input 820, a rotor 822, a splitter 824, and a first output 826 and a second output 828. The TE0 mode at the input 822 propagates to the first output 826 without polarization change. The TM0 mode at the input 822 is converted to the TE1 mode and then converted back to the TE0 mode at the second output 828.

[0047]

[0070] Figures 9A and 9B show another embodiment of the dual-channel switching element. Figure 9A shows a 3D rendering of the switching element. Figure 9B shows a simulated mode profile along a deformable waveguide coupler.

[0048]

[0071] Figure 10 shows a 3D rendering of one embodiment of a dual-channel switching element.

[0072] The paired waveguide couplers of the polarization diversity switch proposed in this disclosure can be actuated by a single shared actuator within each cell. Typically, the footprint of the switch is dominated by the actuator, and the impact on the footprint can be ignored even when using two parallel waveguides. Thus, the proposed polarization diversity switch does not require doubling the chip area, unlike conventional polarization diversity silicon photonic devices that require duplicating the entire PIC to split two polarizations.

Claims

1. circuit board and A row or more of horizontal waveguides arranged on the first layer of the substrate, wherein each row of horizontal waveguides comprises a first horizontal waveguide and a second horizontal waveguide, A row or more of vertical waveguides arranged on the second layer of the substrate, wherein each row of vertical waveguides comprises a first vertical waveguide and a second vertical waveguide, One or more input polarization-independent couplers configured to couple external light to the one or more rows of horizontal waveguides, An input polarization splitter rotor (PSR) coupled to each of the one or more input polarization-independent couplers, wherein each input PSR is configured to split the coupled light into the first and second horizontal waveguides of the one or more rows of horizontal waveguides, A matrix of polarization diversity photonic switches arranged at the intersection of one or more rows of horizontal waveguides and one or more rows of vertical waveguides, wherein the polarization diversity photonic switches are operable to transfer light from the first and second horizontal waveguides of a given row of horizontal waveguides to the first and second vertical waveguides of the intersecting column of vertical waveguides. A photonic integrated circuit (PIC) device equipped with [a specific feature].

2. The PIC device according to claim 1, further comprising an output PSR coupled to each of the one or more rows of vertical waveguides, wherein each output PSR is configured to couple the light from the first and second vertical waveguides to a single output waveguide.

3. The PIC device according to claim 2, further comprising one or more output polarization-independent couplers coupled to each output waveguide.

4. The PIC device according to claim 1, wherein the input PSR is configured to split the input light into two orthogonal polarizations in two separate waveguides, and rotate the polarization of one of the two separate waveguides to achieve the same polarization in the two separate waveguides.

5. The PIC device according to claim 1, wherein the polarization diversity photonic switch is a micro-electromechanical system (MEMS) switch.

6. The PIC device according to claim 1, wherein the polarization diversity photonic switch comprises first and second waveguide couplers disposed on a third layer of the substrate.

7. The PIC device according to claim 6, wherein the third layer is located on the first and second layers.

8. The PIC device according to claim 6, wherein the third layer is located between the first layer and the second layer.

9. The PIC device according to claim 6, wherein the first and second waveguide couplers are configured to be actuated by a MEMS to contact the first and second horizontal waveguides.

10. The PIC device according to claim 6, wherein the first and second waveguide couplers are configured to be actuated by a MEMS to contact the first and second vertical waveguides.

11. The PIC device according to claim 6, wherein the first and second horizontal waveguides are configured to be actuated by a MEMS to contact the first and second waveguide couplers.

12. The PIC device according to claim 6, wherein the first and second vertical waveguides are configured to be actuated by a MEMS to contact the first and second waveguide couplers.

13. The PIC device according to claim 1, wherein the polarization diversity photonic switch comprises overlapping sections of the first and second horizontal waveguides and overlapping sections of the first and second vertical waveguides.

14. The PIC device according to claim 13, wherein the overlapping sections include several bends or curves in each of the horizontal waveguide and the vertical waveguide, thereby enabling alignment of the overlapping portion of the horizontal waveguide and the overlapping portion of the vertical waveguide.

15. The PIC device according to claim 14, wherein the overlapping portion of the horizontal waveguide is parallel to the overlapping portion of the vertical waveguide.

16. The PIC device according to claim 15, wherein the input and output terminals of the horizontal waveguide are orthogonal to the input and output terminals of the vertical waveguide.

17. circuit board and A row or more of horizontal waveguides arranged on the first layer of the substrate, wherein each row of horizontal waveguides comprises a transmit port, a receive port, a first horizontal waveguide, and a second horizontal waveguide, A row or more of vertical waveguides arranged on the second layer of the substrate, wherein each row of vertical waveguides comprises a transmitting port, a receiving port, a first vertical waveguide, and a second vertical waveguide, A transmitting polarization splitter rotor (PSR) coupled to each of the transmitting ports of the horizontal waveguide and each of the transmitting ports of the vertical waveguide, wherein each transmitting PSR is configured to split light into the first and second horizontal waveguides of each of the one or more rows of horizontal waveguides, and into the first and second vertical waveguides of each of the one or more rows of vertical waveguides, A matrix of polarization diversity photonic switches arranged at the intersection of one or more rows of horizontal waveguides and one or more rows of vertical waveguides, wherein the polarization diversity photonic switches are operable to transfer light from the first and second horizontal waveguides corresponding to a given transmitting port to the first and second vertical waveguides corresponding to a pair of receiving ports, and to transfer light from the first and second vertical waveguides corresponding to a given transmitting port to the first and second horizontal waveguides corresponding to a pair of receiving ports, and A photonic integrated circuit (PIC) device equipped with [a specific feature].

18. The PIC device according to claim 17, further comprising a receiving PSR coupled to each of the receiving ports of the horizontal waveguide and each of the receiving ports of the vertical waveguide, wherein each receiving PSR is configured to couple the light from the first and second vertical waveguides or the first and second horizontal waveguides to a single output waveguide.

19. The PIC device according to claim 17, wherein the transmitting PSR is configured to split the light into two orthogonal polarizations in two separate waveguides, and rotate the polarization of one of the two separate waveguides to achieve the same polarization in the two separate waveguides.

20. The PIC device according to claim 17, wherein the polarization diversity photonic switch is a micro-electromechanical system (MEMS) switch.

21. The PIC device according to claim 17, wherein the polarization diversity photonic switch comprises first and second waveguide couplers disposed on a third layer of the substrate, and the first and second waveguide couplers are configured to couple the transmitting port of a horizontal waveguide in a given row to the receiving port of a vertical waveguide in a corresponding column.

22. The PIC device according to claim 21, wherein the polarization diversity photonic switch comprises third and fourth waveguide couplers disposed on the third layer of the substrate, and the first and second waveguide couplers are configured to couple the transmitting ports of vertical waveguides in a given row to the receiving ports of horizontal waveguides in the corresponding row.

23. The PIC device according to claim 21 or 22, wherein the third layer is located on the first and second layers.

24. The PIC device according to claim 21 or 22, wherein the third layer is located between the first layer and the second layer.

25. The PIC device according to claim 21 or 22, wherein the first and second waveguide couplers are configured to be actuated by a MEMS to contact the first and second horizontal waveguides.

26. The PIC device according to claim 21 or 22, wherein the first and second waveguide couplers are configured to be actuated by a MEMS to contact the first and second vertical waveguides.

27. The PIC device according to claim 21 or 22, wherein the first and second horizontal waveguides are configured to be actuated by a MEMS to contact the first and second waveguide couplers.

28. The PIC device according to claim 21 or 22, wherein the first and second vertical waveguides are configured to be actuated by a MEMS to contact the first and second waveguide couplers.

29. The PIC device according to claim 17, wherein the polarization diversity photonic switch comprises overlapping sections of the first and second horizontal waveguides and overlapping sections of the first and second vertical waveguides.

30. The PIC device according to claim 29, wherein the overlapping sections include several bends or curves in each of the horizontal waveguide and the vertical waveguide, thereby enabling alignment of the overlapping portion of the horizontal waveguide and the overlapping portion of the vertical waveguide.

31. The PIC device according to claim 30, wherein the overlapping portion of the horizontal waveguide is parallel to the overlapping portion of the vertical waveguide.

32. The PIC device according to claim 31, wherein the input and output terminals of the horizontal waveguide are orthogonal to the input and output terminals of the vertical waveguide.

33. A method for guiding light through a photonic integrated circuit (PIC), The steps include inputting light into a horizontal waveguide in one row on the first layer of the PIC, The steps include dividing the light into first and second horizontal waveguides of the horizontal waveguide of the row, The steps include controlling an array of micro-electromechanical systems (MEMS) photonic switches to transfer light from the first and second horizontal waveguides to the first and second vertical waveguides of a selected row of vertical waveguides, The steps include outputting the light from the selected column of the vertical waveguide and Includes, method.

34. The method according to claim 33, further comprising the step of coupling the light from the first and second vertical waveguides into a single output before outputting the aforementioned light.

35. The method according to claim 33, further comprising the steps of splitting the light into first and second horizontal waveguides with two orthogonal polarizations, and then rotating the polarization of one of the first and second horizontal waveguides to achieve the same polarization in the first and second horizontal waveguides.

Images