Optical switch controllable by vertically moving MEMS structures

Abstract

MEMS-actuated optical switches can be implemented on photonic chips. These switches are small, generally planar, simple to implement, and contain only one moving MEMS component per switch. The switches exhibit low optical loss, require low power to operate, are simple to control, and are easy to integrate with other optical devices. Each switch has two optical waveguides that are optically coupled in the on switch state and uncoupled in the off switch state. An end section or a middle section of one of the two waveguides can translate between the on and off states to affect the coupling. Alternatively, a coupling frustration can translate between the on and off states to affect the coupling.

Description

Technical Field

[0001] (Cross - reference to Related Applications) This application relates to U.S. Patent Application No. 16 / 586,249, filed on September 27, 2019, entitled "Optical Switch Controllable by Vertical Motion MEMS Structure", the entire content of which is incorporated herein by reference for all purposes.

[0002] The present invention relates to an optical switch, and more particularly to a MEMS - actuated optical switch that can be implemented on a photonic chip.

Background Art

[0003] In many integrated photonic applications, a binary optical switch is required to direct light from an input waveguide to one of two output waveguides. In some applications, several binary optical switches are interconnected to form a 1×N - type, N×M - type, or other type of optical switch network. Ideally, a binary optical switch should have low optical loss, require low power to operate, be small, be simple to control, and be easy to integrate with other optical devices, regardless of the output to which the light is coupled.

[0004] Embodiments of systems that may include optical switches include optical detection and ranging (sometimes referred to as laser imaging, detection, and ranging) (LiDAR) and an image projector. Such systems emit or receive collimated optical beams (visible or invisible from a human perspective) in directions that can be controlled with high precision, and these beams often need to be directed or swept to locate or track a target. Similarly, laser communication systems sometimes need to direct optical beams, for example, first to establish a line-of-sight communication channel between two terminals, or later to track whether one or both terminals are moving. Modern optical systems often require small, substantially planar optical switch networks implemented on photonic chips, for example, to drive arrays of emitters for LiDAR and image projectors. For example, see U.S. Patent Publication 2018 / 0175961, entitled "Integrated MEMS Switches for Selectively Coupling Light In and Out of a Waveguide" (the entire contents of which are incorporated herein by reference for any purpose).

[0005] A common method for implementing optical switches within integrated photonic circuits involves the use of a Mach-Zehnder interferometer and a phase shifter. In such a circuit, the relative phase of two arms directs the light to a selected output. Phase shift can be implemented and controlled by several known methods, such as thermal tuning. A phase shifter-based Mach-Zehnder switch is an analog device capable of switching any amount of power between two outputs. While this is advantageous for many applications, for applications where dual switching is desired, very precise control of the phase between the two arms is required to obtain low loss and good attenuation. Such precise phase control requires a complex control system, especially when environmental factors such as temperature can affect the phase of light propagation.

[0006] "Large-scale broadband digital silicon photonic switches with vertical adiabatic couplers" by Tae Joon Seok, et al., published in January 2016 in Optica, Vol. 3, No. 1, pp. 64-70 ("Seok"), and "Large-scale broadband digital silicon photonic switches with vertical adiabatic couplers: supplemental material" by Tae Joon Seok, et al., published in "Seok Supplement" ("Large-scale broadband digital silicon photonic switches with vertical adiabatic couplers: supplemental material") ("Seok Supplement"), describe MEMS-operated optical switching matrices consisting of multiple perpendicularly intersecting, typically uncoupled waveguides. "Large-scale silicon photonic switches with movable directional couplers" by Sangyoon Han, et al., published in April 2015 in Optica, Vol. 2, No. 4, pp. 370-375 ("Han"), discloses another MEMS-operated optical switching matrix consisting of multiple perpendicularly intersecting, typically uncoupled waveguides. In Seok and Han, individual switch cells are placed at each waveguide intersection. When a switch cell is activated, it couples the two intersecting waveguides in both directions. Thus, the switching matrix can act as a crossbar switch, where each row of the switching matrix can be coupled to a desired column of the switching matrix.

[0007] However, each Seok switch cell requires a pair of back-to-back adiabatic couplers on a separate MEMS actuator, and each Han switch cell requires a pair of back-to-back resonant couplers on a MEMS actuator. In each case, the two couplers are distinct from the intersecting waveguides, and in Seok, the two couplers can be operated independently. To turn on the switch cell, both couplers must be moved so that the two couplers are each close to the separate ones of the two intersecting waveguides. In the ON state, light from one of the two intersecting waveguides couples into one of the couplers. The light then propagates to the other coupler, and then the light couples from the other coupler into the other of the two intersecting waveguides. Thus, two transient couplings are required within the ON switch cell, which results in losses. The two perpendicular waveguides are stationary. Only the couplers move. A coupler is not physically part of any waveguide. A coupler does not extend beyond a switch cell. In contrast, each waveguide extends beyond a switch cell in both directions. Each switch cell is bidirectional; that is, light can propagate simultaneously in either direction or both directions through the on-switch cell between two intersecting waveguides. However, a simpler optical switch with lower losses, which can be implemented on a photonic chip, would be preferable. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] U.S. Patent Publication No. 2018 / 0175961 [Overview of the Initiative] [Means for solving the problem]

[0009] One embodiment of the present invention provides an optical switch having a certain design wavelength. The optical switch includes a photonic chip. A first input / output port includes a first optical waveguide located on the photonic chip. A second input / output port includes a second optical waveguide located on the photonic chip, distinctly different from the first optical waveguide. A first end portion of the second optical waveguide is located adjacent to the middle portion of the first optical waveguide.

[0010] A MEMS structure is placed on a photonic chip. The MEMS structure has a translationable portion configured to translate in response to a control signal.

[0011] The translationable optical component includes either (a) the middle portion of the first optical waveguide or (b) the first end portion of the second optical waveguide. That is, in any given embodiment, the translationable optical component includes either (a) the middle portion of the first optical waveguide or (b) the first end portion of the second optical waveguide, but not both (a) and (b).

[0012] The translationable portion of the MEMS structure is mechanically coupled to a translationable optical component, thereby configured to translate between at least a first (on) position and a second (off) position. In the first (on) position, the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide are close enough to transiently couple with each other with a coupling efficiency of at least about 85% at the design wavelength. In the second (off) position, the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide are far enough apart to transiently couple with each other with a coupling efficiency of up to about 10% at the design wavelength.

[0013] In any embodiment, when a translatable optical component is in a first position, a first input / output port may be optically coupled to a second input / output port via a single transient coupling. The single transient coupling may be between the middle portion of the first optical waveguide and the first end portion of the second optical waveguide. Strictly speaking, either (a) the middle portion of the first optical waveguide or (b) the first end portion of the second optical waveguide is configured to be translatable. That is, in any given embodiment, either (a) the middle portion of the first optical waveguide is configured to be translatable, or (b) the first end portion of the second optical waveguide is configured to be translatable, but not both (a) and (b) are necessarily the case.

[0014] In any embodiment, the optical switch may have an outer boundary defining a minimum-sized rectangular area, including a translatable optical component and a MEMS structure. The first and second input / output ports may be arranged outside the outer boundary. Each end of the first optical waveguide may be arranged outside the outer boundary. The intermediate portion of the first optical waveguide may be located within the outer boundary. The first end portion of the second optical waveguide may be located within the outer boundary. The second end of the second optical waveguide, opposite the first end portion, may be located outside the outer boundary. The MEMS structure may be located within the outer boundary.

[0015] In any embodiment, the translatable optical component may include an intermediate portion of the first optical waveguide.

[0016] In some embodiments, at both the first and second positions, the intermediate portion of the first optical waveguide is aligned above the first end portion of the second optical waveguide when viewed normal to the photonic chip. The intermediate portion of the first optical waveguide may be configured to translate relative to the photonic chip in a plane that crosses the first end portion of the second optical waveguide.

[0017] In some embodiments, the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide are configured such that, when the intermediate portion of the first optical waveguide is in a first position, the intermediate portion of the first optical waveguide resonantly and optically couples with the first end portion of the second optical waveguide with a coupling efficiency of at least about 85% at the design wavelength.

[0018] In some embodiments, the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide are configured such that, when the intermediate portion of the first optical waveguide is in a first position, the intermediate portion of the first optical waveguide couples adiabatically and optically with a coupling efficiency of at least about 85% at the design wavelength.

[0019] In some embodiments, at both the first and second positions, the intermediate portion of the first optical waveguide is displaced laterally from the first end portion of the second optical waveguide when viewed normal to the photonic chip. The intermediate portion of the first optical waveguide may be configured to translate in a plane that does not cross the first end portion of the second optical waveguide.

[0020] In some embodiments, the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide are configured such that, when the intermediate portion of the first optical waveguide is in a first position, the intermediate portion of the first optical waveguide resonantly and optically couples with the first end portion of the second optical waveguide with a coupling efficiency of at least about 85% at the design wavelength.

[0021] In some embodiments, the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide are configured such that, when the intermediate portion of the first optical waveguide is in a first position, the intermediate portion of the first optical waveguide couples adiabatically and optically with a coupling efficiency of at least about 85% at the design wavelength.

[0022] In some embodiments, the translationable optical component includes a first end portion of a second optical waveguide.

[0023] In some embodiments, at both the first position and the second position, the first end portion of the second optical waveguide is aligned above the middle portion of the first optical waveguide. The first end portion of the second optical waveguide may be configured to translate within a plane transverse to the middle portion of the first optical waveguide with respect to the photonic chip.

[0024] In some embodiments, the middle portion of the first optical waveguide and the first end portion of the second optical waveguide are configured such that when the middle portion of the first optical waveguide is at the first position, the middle portion of the first optical waveguide resonantly and optically couples to the first end portion of the second optical waveguide with at least about 85% coupling efficiency at the design wavelength.

[0025] In some embodiments, the middle portion of the first optical waveguide and the first end portion of the second optical waveguide are configured such that when the middle portion of the first optical waveguide is at the first position, the middle portion of the first optical waveguide adiabatically and optically couples to the first end portion of the second optical waveguide with at least about 85% coupling efficiency at the design wavelength.

[0026] In some embodiments, at both the first position and the second position, when viewed in the normal direction with respect to the photonic chip, the first end portion of the second optical waveguide is laterally displaced from the middle portion of the first optical waveguide. The first end portion of the second optical waveguide may be configured to translate within a plane that does not cross the middle portion of the first optical waveguide.

[0027] In some embodiments, the middle portion of the first optical waveguide and the first end portion of the second optical waveguide are configured such that when the middle portion of the first optical waveguide is at the first position, the middle portion of the first optical waveguide resonantly and optically couples to the first end portion of the second optical waveguide with at least about 85% coupling efficiency at the design wavelength.

[0028] In some embodiments, the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide are configured such that, when the intermediate portion of the first optical waveguide is in a first position, the intermediate portion of the first optical waveguide couples adiabatically and optically with a coupling efficiency of at least about 85% at the design wavelength.

[0029] Another embodiment of the present invention provides an optical switch having a certain design wavelength. The optical switch comprises a photonic chip and a translationable optically coupled frustrator.

[0030] A first optical waveguide is placed on a photonic chip. The first optical waveguide has an intermediate portion.

[0031] A second optical waveguide, distinct from the first optical waveguide, is placed on the photonic chip. The second optical waveguide has a first end portion, which is immovable relative to the middle portion of the first optical waveguide. The first end portion is sufficiently close to the middle portion of the first optical waveguide to transiently couple with the middle portion of the first optical waveguide with a coupling efficiency of at least approximately 85% at the design wavelength, in the absence of an optical coupling frustrator.

[0032] A MEMS structure is placed on a photonic chip. The MEMS structure has a translationable portion that is mechanically coupled to an optically coupled frustrator. The MEMS structure is configured to translate the optically coupled frustrator between at least a first position and a second position in response to a control signal. The first position is close to at least one of the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide. That is, at the first position, the optically coupled frustrator is close to the intermediate portion of the first optical waveguide and / or the first end portion of the second optical waveguide. The second position is spaced away from at least one of the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide.

[0033] At the first position, the optical coupling frustrator is positioned sufficiently close to the intermediate portion of the first optical waveguide and / or the first end portion of the second optical waveguide to prevent transient coupling between the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide, with a coupling efficiency of more than approximately 10% at the design wavelength. At the second position, the optical coupling frustrator is positioned sufficiently far from the intermediate portion of the first optical waveguide and / or the first end portion of the second optical waveguide to allow transient coupling between the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide, with a coupling efficiency of at least approximately 85% at the design wavelength.

[0034] In some embodiments, at both the first and second positions, the optically coupled frustrator is aligned above at least a portion of at least one of the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide when viewed in the direction normal to the photonic chip.

[0035] In some embodiments, at both the first and second positions, the optically coupled frustrator is laterally displaced from the middle portion of the first optical waveguide and the first end portion of the second optical waveguide when viewed in the direction normal to the photonic chip.

[0036] In some embodiments, at a first position, the optically coupled frustrator is close to the middle portion of the first optical waveguide, and at a second position, the optically coupled frustrator is spaced away from the middle portion of the first optical waveguide.

[0037] In some embodiments, at a first position, the optically coupled frustrator is close to the first end portion of the second optical waveguide, and at a second position, the optically coupled frustrator is spaced away from the first end portion of the second optical waveguide. [Brief explanation of the drawing]

[0038] The present invention will be better understood by referring to the following detailed description of specific embodiments in conjunction with the drawings.

[0039] [Figure 1] Figure 1 is a perspective view illustrating the general principle of an optical switch according to several embodiments of the present invention. Subsequent drawings illustrate various aspects of individual embodiments of the switch shown in Figure 1.

[0040] [Figure 2] Figure 2 is a perspective view of one embodiment of the optical switch shown in Figure 1, in which one end of one waveguide is positioned directly above the middle portion of the other waveguide, according to one embodiment of the present invention.

[0041] [Figure 3] Figure 3 is a side view of the optical switch shown in Figure 2, according to one embodiment of the present invention.

[0042] [Figure 4] Figure 4 is a perspective view of another embodiment of the optical switch of Figure 1, according to one embodiment of the present invention, in which the end of one waveguide is positioned directly below the middle portion of the other waveguide.

[0043] [Figure 5] Figure 5 is a side view of the optical switch shown in Figure 4, according to one embodiment of the present invention.

[0044] [Figure 6] Figure 6 is a perspective view of yet another embodiment of the optical switch of Figure 1, according to one embodiment of the present invention, in which the end of one waveguide is aligned above the middle portion of the other waveguide. Figure 6 shows the optical switch in the OFF state.

[0045] [Figure 7] Figure 7 is a side view of the optical switch in Figure 6 in the OFF state, according to one embodiment of the present invention.

[0046] [Figure 8] Figure 8 is a perspective view of the optical switch shown in Figures 6 and 7, illustrating an ON state of the optical switch according to one embodiment of the present invention.

[0047] [Figure 9] Figure 9 is a side view of the optical switch shown in Figure 6-8 in the ON state, according to one embodiment of the present invention.

[0048] [Figure 10] Figures 10 and 11 are individual cross-sectional views of the optical switch shown in Figure 6-9 according to one embodiment of the present invention. Figure 10 shows the optical switch in the OFF state, and Figure 11 shows the optical switch in the ON state. [Figure 11] Figures 10 and 11 are individual cross-sectional views of the optical switch shown in Figure 6-9 according to one embodiment of the present invention. Figure 10 shows the optical switch in the OFF state, and Figure 11 shows the optical switch in the ON state.

[0049] [Figure 12] Figures 12 and 13 are individual perspective views of the optical switch of Figure 6-11, according to one embodiment of the present invention, where the translationable portion of the MEMS structure is shown in wireframe. Figure 12 shows the optical switch in the OFF state, and Figure 13 shows the optical switch in the ON state. [Figure 13] Figures 12 and 13 are individual perspective views of the optical switch of Figure 6-11, according to one embodiment of the present invention, where the translationable portion of the MEMS structure is shown in wireframe. Figure 12 shows the optical switch in the OFF state, and Figure 13 shows the optical switch in the ON state.

[0050] [Figure 14] Figures 14 and 15 are individual perspective views of another embodiment of the optical switch of Figure 1, according to one embodiment of the present invention, in which the end of one waveguide is positioned laterally displaced from the middle portion of the other waveguide. Figure 14 shows the optical switch in the off state, and Figure 15 shows the optical switch in the on state. [Figure 15]Figures 14 and 15 are individual perspective views of another embodiment of the optical switch of Figure 1, according to one embodiment of the present invention, in which the end of one waveguide is positioned laterally displaced from the middle portion of the other waveguide. Figure 14 shows the optical switch in the off state, and Figure 15 shows the optical switch in the on state.

[0051] [Figure 16] Figure 16 is a perspective view of an optical switch according to an arbitrary embodiment of the present invention, in which a translatable optical component translates in a plane that crosses another waveguide.

[0052] [Figure 17] Figure 17 is a perspective view of an optical switch including a resonant coupler according to several embodiments of the present invention.

[0053] [Figure 18] Figure 18 is a perspective view of an optical switch, including an adiabatic coupler, according to several embodiments of the present invention.

[0054] [Figure 19] Figure 19 is a perspective view of yet another embodiment of the optical switch in Figure 1, in which a vertically translatable coupling frustrator is used to control whether two optical waveguides are coupled, according to one embodiment of the present invention.

[0055] [Figure 20] Figures 20, 21, and 22 are perspective views of alternative embodiments of the optical switch in Figure 19, according to individual embodiments of the present invention. [Figure 21] Figures 20, 21, and 22 are perspective views of alternative embodiments of the optical switch in Figure 19, according to individual embodiments of the present invention. [Figure 22] Figures 20, 21, and 22 are perspective views of alternative embodiments of the optical switch in Figure 19, according to individual embodiments of the present invention.

[0056] [Figure 23]Figures 23 and 24 show the results of computer simulations of the optical switch in Figure 19 in the ON and OFF states, respectively. [Figure 24] Figures 23 and 24 show the results of computer simulations of the optical switch in Figure 19 in the ON and OFF states, respectively.

[0057] [Figure 25] Figures 25 and 26 are perspective views of yet another embodiment of the optical switch of Figure 1, according to one embodiment of the present invention, in which the adiabatic coupler is positioned below the intermediate portion of the other waveguide. In Figures 25 and 26, the translationable portion of the MEMS structure is shown in wireframe. Figure 25 shows the optical switch in the off state, and Figure 26 shows the optical switch in the on state. [Figure 26] Figures 25 and 26 are perspective views of yet another embodiment of the optical switch of Figure 1, according to one embodiment of the present invention, in which the adiabatic coupler is positioned below the intermediate portion of the other waveguide. In Figures 25 and 26, the translationable portion of the MEMS structure is shown in wireframe. Figure 25 shows the optical switch in the off state, and Figure 26 shows the optical switch in the on state.

[0058] [Figure 27] Figures 27, 28, 29, and 30 show the results of computer simulations of the optical switches shown in Figures 25 and 26. [Figure 28] Figures 27, 28, 29, and 30 show the results of computer simulations of the optical switches shown in Figures 25 and 26. [Figure 29] Figures 27, 28, 29, and 30 show the results of computer simulations of the optical switches shown in Figures 25 and 26. [Figure 30] Figures 27, 28, 29, and 30 show the results of computer simulations of the optical switches shown in Figures 25 and 26.

[0059] [Figure 31]Figure 31 is a top view of a portion of a MEMS structure for translating a waveguide or coupled frustrator according to one embodiment of the present invention, Figure 32 is a side view thereof (optical switch in the off state), Figure 33 is a side view thereof (optical switch in the on state), and Figure 34 is a cross-sectional view thereof. The MEMS structure may be used in any optical switch described herein. [Figure 32] Figure 31 is a top view of a portion of a MEMS structure for translating a waveguide or coupled frustrator according to one embodiment of the present invention, Figure 32 is a side view thereof (optical switch in the off state), Figure 33 is a side view thereof (optical switch in the on state), and Figure 34 is a cross-sectional view thereof. The MEMS structure may be used in any optical switch described herein. [Figure 33] Figure 31 is a top view of a portion of a MEMS structure for translating a waveguide or coupled frustrator according to one embodiment of the present invention, Figure 32 is a side view thereof (optical switch in the off state), Figure 33 is a side view thereof (optical switch in the on state), and Figure 34 is a cross-sectional view thereof. The MEMS structure may be used in any optical switch described herein. [Figure 34] Figure 31 is a top view of a portion of a MEMS structure for translating a waveguide or coupled frustrator according to one embodiment of the present invention, Figure 32 is a side view thereof (optical switch in the off state), Figure 33 is a side view thereof (optical switch in the on state), and Figure 34 is a cross-sectional view thereof. The MEMS structure may be used in any optical switch described herein.

[0060] [Figure 35] Figure 35 is a top view of a portion of a MEMS structure for translating a waveguide or coupled frustrator according to another embodiment of the present invention, and Figure 36 is a cross-sectional view thereof. The MEMS structure may be used in any optical switch described herein. [Figure 36]Figure 35 is a top view of a portion of a MEMS structure for translating a waveguide or coupled frustrator according to another embodiment of the present invention, and Figure 36 is a cross-sectional view thereof. The MEMS structure may be used in any optical switch described herein.

[0061] [Figure 37] Figures 37 and 38 are side views of a MEMS structure in separate off and on positions according to another embodiment of the present invention. The MEMS structure may be used in any optical switch described herein. [Figure 38] Figures 37 and 38 are side views of a MEMS structure in separate off and on positions according to another embodiment of the present invention. The MEMS structure may be used in any optical switch described herein.

[0062] [Figure 39] Figure 39 is a top view of a MEMS structure in the ON position according to another embodiment of the present invention. The MEMS structure may be used in any optical switch described herein. [Modes for carrying out the invention]

[0063] Detailed description of specific embodiments Embodiments of the present invention provide MEMS-operated optical switches that can be mounted on a photonic chip. These optical switches are small, substantially planar, easy to mount, contain only one movable MEMS component per optical switch, and, unlike Seok or Han, require only one transient coupling per on-optical switch. The switches exhibit low optical loss, require low power to operate, are small, easy to control, and easily integrate with other optical devices. Optical Switch - Overview

[0064] Figure 1 is a perspective view of an optical switch 100 fabricated on a photonic chip 102 according to several embodiments of the present invention. The general principle of the optical switch 100 is described with reference to Figure 1, and various aspects of the optical switch 100 are described below with reference to other drawings. These aspects include (a) whether the end portion of one waveguide is adjacent to or above the middle portion of the other waveguide, (b) whether the end portion is above or below the middle portion, (c) whether the two waveguides are resonantly or adiabatically coupled in the ON state, (d) the number of possible switch states (e.g., a binary on / off optical switch has two states), (e) the optical components that translate to change the switch state, and (f) the properties of the translatable optical components (e.g., whether it is an optical coupler or a coupling frustrator). These aspects can be combined in various ways, some of which are described herein. These aspects and combinations of aspects may vary between embodiments.

[0065] The optical switch 100 includes two optical waveguides 104 and 106 and has a design wavelength that may encompass a range of wavelengths. Waveguides 104 and 106 are mounted on a photonic chip 102 and positioned above, above, or below the surface 108 of the photonic chip 102. Waveguides 104 and 106 are fabricated from suitable materials, as is well known in the art, and are sized and machined to facilitate the propagation of optical signals within the design wavelength with low loss. A translationable optical component located on the other waveguide side.

[0066] The relative arrangement of the end portion 110 of waveguide 106 and the intermediate portion 112 of the other waveguide 104 represents one aspect of the optical switch 100, which may differ among various embodiments. In the embodiment shown in Figure 1, the end portion 110 of waveguide 106 and the intermediate portion 112 of the other waveguide 104 are positioned laterally adjacent to each other when viewed from above (normal to the surface 108) of the photonic chip 102. That is, at least in the ON state, the end portion 110 of waveguide 106 is positioned at the same distance from the surface 108 of the photonic chip 102 as the intermediate portion 112 of the other waveguide 104 is positioned from the surface 108, and the end portion 110 of waveguide 106 is displaced at a lateral distance 114 from the other waveguide 104 when viewed from above (normal to the surface 108). Therefore, when viewed from above in a direction normal to the surface 108, the end portion 110 of one waveguide 106 and the intermediate portion 112 of the other waveguide 104 are located side by side on the surface 108 of the photonic chip 102. A translationable optical element positioned above another waveguide.

[0067] However, in some other embodiments, as illustrated by the optical switch 200 shown in Figures 2 and 3, the end portion 110 may be positioned and aligned above the intermediate portion 112 of the other waveguide 104 when viewed from above, normal to the surface 108. The support structure 202 lifts and supports waveguide 106 above the other waveguide 104. Optionally, waveguide 106 can return to the surface 108 beyond the optical switch 200. It should be noted that in some applications, the two waveguides 104 and 106 do not need to be located on the same or similar layers, as in Seok and Han. It should also be noted that the fact that the two waveguides 104 and 106 do not need to be on the same or similar layers has made it possible to implement an optical switch with only a single coupler per switch cell, rather than two couplers per switch cell, as in Seok and Han.

[0068] In some other embodiments, as illustrated by the optical switch 400 shown in Figures 4 and 5, the end portion 110 of the optical waveguide 106 may be positioned below and aligned with the intermediate portion 112 of the other waveguide 104 when viewed from above, normal to the surface 108, as will be discussed in more detail herein.

[0069] Returning to Figure 1, most optical switches 100 have exactly two states, namely, typically "on" and "off," and are binary in that they switch the light from the input path 116 (one of the two optical waveguides 104 or 106) to exactly one of the two output paths 118 or 120. One output path 118 may be a continuation of the input path 116 of the optical waveguide 104, and the other output path 120 typically follows the other optical waveguide 106. Both the input path 118 and the output paths 120 extend beyond the optical switch 100. However, one of the two optical paths 118 or 120 terminates within the optical switch 100; that is, only one end of the two optical paths 118 or 120 is located within the optical switch 100. In contrast, back-to-back couplers in Seok or Han switch cells do not extend beyond the switch cell. In other words, both ends of each back-to-back coupler in Seok and Han are positioned together with their individual switch cells.

[0070] The optical switch 100 includes at least first and second input / output ports 130 and 132, optionally a third input / output port 134, and optionally a fourth input / output port (not shown). Regardless of the number of input / output ports on a given optical switch 100, the input / output ports 130-134 are representative. The input / output ports 130-134 can be defined by cross-sections of their individual optical waveguides 104 and 106, as shown by dashed lines. The input / output ports 130-134 serve as separate interfaces between the optical switch 100 and other optical components such as a light source, a photodetector, or another optical switch (not shown) that is distinctly different from the optical switch 100. Each input / output port 130-134 provides means for obtaining optical signals from, to, or into or out of the optical switch 100 to, another optical component, i.e., something other than the optical switch 100. Input / output ports 130-134 are used to inject light into the optical switch 100 and then to receive the light.

[0071] The optical switch 100 controls how light received through one of the input / output ports 130-134 is directed to the other input / output ports 130-134. As described, the input / output ports 130-134 serve as separate interfaces to the optical switch 100. Therefore, the input / output ports 130-134 are not components through which light propagates into the optical switch 100. Under this definition of input / output ports, the translatable optical couplers in Seok or Han are not input / output ports because each translatable optical coupler in Seok or Han is entirely internal to a given optical switch cell, and each translatable optical coupler in Seok or Han merely transmits light within the optical switch cell, and not between the optical switch cell and another optical component. The translatable optical couplers in Seok and Han are not interfaces between the optical switch cell and other optical components. The on / off nature of the optical switch 100 can be considered to describe whether or not the light from the input path 116 is switched to the output path 120.

[0072] In the ON state, the two optical waveguides 104 and 106 transiently couple to each other at the design wavelength with an efficiency of at least about 85%, so that depending on waveguide 104 and / or 106 acting as input waveguides, light propagating along input waveguide 104 couples with the other waveguide 106, or vice versa, or bidirectional coupling occurs. The coupling occurs within region 122. The coupling can be resonant coupling and / or adiabatic coupling.

[0073] In the off state, the two waveguides are either not transiently coupled, or transiently coupled with an efficiency of less than approximately 10%, so that light propagating along one of the two waveguides 104 or 106 is substantially not coupled to the other waveguide, but instead continues to propagate along the input waveguide. As used herein, a coupling efficiency of less than approximately 10% is considered non-coupled. When the optical switch 100 is in the off state, light from the input path 116 propagates along waveguide 104 to the output path 118. The output path 118 may continue to another optical switch (not shown) or another optical element (not shown), or the output path 118 may terminate beyond the optical switch 100.

[0074] Although discussed in the context of a binary optical switch, the principles disclosed herein may, with necessary modifications (mutatis mutandis), be used to construct an optical switch that splits input light between output paths according to a control signal and / or optical switch with two or more states and / or optical paths, such that each output path of multiple output paths simultaneously receives more than a non-zero portion, e.g., more than 10% of the input light. Several such non-binary optical switches are described herein. The number of states of the optical switch is one aspect of the optical switch 100. Another aspect of the optical switch 100 is whether the input light is switched to substantially only one output path, or alternatively, whether the input light is split among multiple output paths.

[0075] Returning to Figure 1, the MEMS structure 124 is positioned on or within the photonic chip 102. At least a portion (not shown) of the MEMS structure 124 is configured to translate along an axis perpendicular to the surface 108 of the photonic chip 102 in response to a control signal 128, as indicated by the double arrow 126. The MEMS structure 124 may include a flexed portion and spaced electrodes (not shown) that are electrostatically attracted to each other in response to a control voltage (derived from the control signal 128) applied to electrodes or an electromagnetic structure to translate the translatable portion of the MEMS structure 124.

[0076] The translationable portion of the MEMS structure 124 is mechanically coupled to a translationable optical component (not shown in Figure 1, but described in detail herein) and configured to translate the translationable optical component along axis 126. Translation of the translationable optical component from a first position to a second position changes the optical switch 100 from one state to another, for example, from an off state to an on state. In Figure 1, the MEMS structure 124 is shown to the right of both waveguides 104 and 106, but in some embodiments (described with reference to other drawings), the MEMS structure 124 is located to the left of one or both of waveguides 104 and 106 and / or above or below one or both of waveguides 104 and 106.

[0077] As described, one side of the optical switch 100 involves the relative arrangement of the end portion 110 of one waveguide 106 and the intermediate portion 112 of the other waveguide 104. Figure 6 illustrates an optical switch 600 in which the end portion 110 of one waveguide 106 is aligned above the intermediate portion 112 of the other waveguide 104. Thus, in this embodiment, the arrangement side of the end portion 110 and the intermediate portion 112 can be described as being aligned upward.

[0078] In this embodiment, the end portion 110 is mechanically coupled to the MEMS structure 124 (omitted from Figure 6 for clarity) and translates in response to the translation of the translationable portion of the MEMS structure 124, as indicated by the double arrow 602. Thus, in this embodiment, the end portion 110 is the aforementioned translationable optical component. The end portion 110 translates between (a) an off position distal to the intermediate portion 112 (as illustrated in Figures 6 and 7) and (b) an on position close to the intermediate portion 112 (as illustrated in Figures 8 and 9). The flexible portion 604 facilitates the translation of the end portion 110, while the rest of the waveguide 106 remains immobile relative to the photonic chip 102.

[0079] In the off position (Figures 6 and 7), the end portion 110 is sufficiently far from the intermediate portion 112 to prevent coupling between the end portion 110 and the intermediate portion 112. However, in the on position (Figures 8 and 9), the end portion 110 is sufficiently close to the intermediate portion 112 to couple the end portion 110 and the intermediate portion 112 with a coupling efficiency of at least about 85% at the design wavelength, although it is not necessarily in close contact with it.

[0080] In this embodiment, the end portion 110 of waveguide 106 remains perpendicularly aligned above the intermediate portion 112 of the other waveguide 104 as it translates, regardless of whether the end portion 110 is in the off position or the on position. Therefore, the end portion 110 can be described as translating perpendicularly above the intermediate portion 112 of the other waveguide 104.

[0081] The MEMS structure 124 can define a volume that encloses the end portion 110 of waveguide 106 and the intermediate portion 112 of the other waveguide 104, as shown in Figure 6 by a rectangular prism 606 with dashed lines. Figures 10 and 11 are cross-sectional views of the MEMS structure 124 as viewed from a cross-sectional plane 608 (Figure 6). Figures 12 and 13 are simplified perspective views of the optical switch 600 with a translatable portion of the MEMS structure 124 shown as a wireframe. Figures 10 and 12 show the MEMS structure 124 when the end portion 110 is in the off position, i.e., when the optical switch 600 is in the off state, and Figures 11 and 13 show the MEMS structure 124 when the end portion 110 is in the on position, i.e., when the optical switch 600 is in the on state.

[0082] As shown in Figures 10 and 11, the MEMS structure 124 may include a counter electrode 1000 that can be charged to an appropriate voltage and induced to promote the translation of the end portion 110 between the off and on positions. The MEMS structure 124 should include a mechanical stopper 1002 to limit the movement of the end portion 110, i.e., to ensure a small gap between the end portion 110 and the intermediate portion 112 in the on position. The stopper should also be designed to have a minimal contact area with the movable MEMS element to prevent "static friction" (adhesion of van der Waals or Miller charge base). The electrode 1000, the stopper 1002, and other details are omitted from the wireframe diagrams (Figures 12 and 13) for simplification. Translation of the middle portion of the waveguide

[0083] As discussed with respect to Figures 4 and 5, in the optical switch 400, the end portion 110 of waveguide 106 is positioned below and aligned with the intermediate portion 112 of the other waveguide 104. The support structure 202 lifts and supports waveguide 104 above waveguide 106. In this embodiment, the intermediate portion 112 translates between an off position (shown by a solid line) and an on position (shown by a dashed line in Figure 5), as indicated by the double arrow 402. In such an embodiment, a translatable portion of the MEMS structure 124 (not shown in Figures 4 and 5 for clarity) is mechanically coupled to the intermediate portion 112, causing the intermediate portion 112 to translate between the off and on positions. In such an embodiment, the intermediate portion 112 of waveguide 104 is supported and translated by the translatable portion of the MEMS structure 124. Therefore, Figures 12 and 13 may be modified to place the intermediate portion 112 on the wireframe and the end portion 110 of the waveguide 106 below the wireframe. In other respects, the optical switch 400 is similar to the optical switch 600 described herein. A translationable optical component located on the other waveguide side.

[0084] Figures 14 and 15 illustrate an optical switch 1400 similar to the optical switch 600 shown in Figure 6-13, except that the end portion 110 of waveguide 106 is not aligned above the middle portion 112 of the other waveguide 104. Instead, according to this embodiment, in both the ON and OFF positions, the end portion 110 is displaced laterally from the other waveguide 104 at a distance of 114 when viewed from above (normal to the surface 108).

[0085] Figure 14 shows the optical switch 1400 in the OFF state, and Figure 15 shows the optical switch 1400 in the ON state. In the optical switch 1400, as in the optical switch 600 described with respect to Figure 6-13, the end portion 110 is translated vertically as indicated by the double arrow 1402. However, the end portion 110 of waveguide 106 remains not perpendicularly aligned with the intermediate portion 112 of the other waveguide 104, regardless of whether the end portion 110 is in the OFF or ON position. In this embodiment, in the ON state, the end portion 110 of waveguide 106 and the intermediate portion 112 of the other waveguide 104 are coupled laterally as indicated by the coupling region 122 in Figure 15. Thus, in this embodiment, the end portion 110 is the aforementioned translatable optical component.

[0086] A MEMS structure similar to the MEMS structure 124 shown in Figure 10-13 (not shown in Figures 14 and 15 for clarity) may have an end portion 110 and an intermediate portion 112 that are displaced laterally from each other, but may also be used to translate the end portion 110. The MEMS structure 124 described with respect to Figure 10-13 has flexures on both sides of a translatable optical component (coupler), but if the translatable optical component is translated in a plane that does not cross another waveguide (as in Figures 14 and 15), the MEMS structure 124 may have a flexure on only one side, and the MEMS structure 124 may be anchored on only one side, as described below with respect to Figures 35 and 36. The end portion 110 can be described as translating perpendicularly adjacent to the intermediate portion 112 of the other waveguide 104. Therefore, in this embodiment, the arrangement sides of the end portion 110 and the intermediate portion 112 can be described as adjacent, side-by-side, or not aligned.

[0087] Referring to Figure 1, if waveguide 104 continues to another optical switch (not shown) or another optical component (not shown), waveguide 104 may be referred to as a “bus” waveguide, and the other waveguide 106 may be referred to as a “pick-off” waveguide because, when optical switch 100 is in the ON state, the other waveguide 106 “picks up” light from the bus waveguide. As described above, one aspect of optical switch 100 is the relative vertical position of the intermediate portion 112 of the bus waveguide and the end portion 110 of the pick-off waveguide. Figures 2, 3, and 6-14 show optical switches 200, 600, and 1400 in which the end portion 110 of the pick-off waveguide 106 is positioned higher than the intermediate portion 112 of the bus waveguide 104 relative to the photonic chip 102, at least when it is OFF. On the other hand, Figures 4 and 5 show an optical switch 400 in which the end portion 110 of the input waveguide 106 is positioned lower than the intermediate portion 112 of the bus waveguide 104.

[0088] Another aspect of the optical switch 100 is the relative horizontal position of the intermediate portion 112 of the bus waveguide and the end portion 110 of the intake waveguide. Figure 2-13 shows optical switches 200, 400, and 600 in which the end portion 110 of the intake waveguide is aligned perpendicularly with the intermediate portion 112 of the bus waveguide. In these embodiments, the translatable optical component, whether the end portion 110 or the intermediate portion 112, translates in a plane 1600 that crosses the other waveguide, as shown in Figure 16. The translatable optical component translates along the axis, as indicated by the double arrow 1602. On the other hand, Figures 14 and 15 show optical switch 1400 in which the end portion 110 of the intake waveguide is displaced laterally and is therefore not aligned perpendicularly with the intermediate portion 112 of the bus waveguide. In this embodiment, the translatable optical component translates within a plane that does not cross the other waveguide. Translationable optical components

[0089] Another aspect of the optical switch 100 involves the properties of its translational optical components, which can affect the type of coupling (adiabatic or resonant) that occurs when the optical switch is in the ON position. Figure 17 is a perspective view of the optical switch, where the end portion 110 of one waveguide 106 and the intermediate portion 112 of the other waveguide 104 have approximately equal effective refractive indices at the design wavelength. In this case, when the end portion 110 and the intermediate portion 112 are in the ON position, the coupling between the end portion 110 and the intermediate portion 112 is resonant.

[0090] Several factors, including the material and dimensions, affect the refractive index. Therefore, one way to make the effective refractive indices approximately equal is to manufacture the end portion 110 and the intermediate portion 112 from the same material and make their individual dimensions approximately equal. However, if the end portion 110 and the intermediate portion 112 are made from different materials, their individual effective refractive indices can be made approximately equal by adjusting their individual dimensions, as is well known to those skilled in the art. Similarly, if the individual dimensions of the end portion 110 and the intermediate portion 112 are different, they can be made to have approximately equal effective refractive indices by careful selection of their individual materials.

[0091] In a resonant coupler, optical power is transmitted between two waveguides 104 and 106 due to symmetric and asymmetric modes having different propagation velocities. If the length of the resonant coupler is appropriately selected, the input power can be arbitrarily divided between the output waveguides, as is known to those skilled in the art. Unless otherwise shown, in the embodiments described herein, the resonant coupler is designed to transmit the power completely, as practically possible, and therefore the optical switch can be considered an on / off switch. However, in other embodiments, the length of the resonant coupler is selected such that, when the optical switch is in the ON state, less than a certain amount of power is transmitted, as practically possible, and the remainder of the power continues through the other waveguide.

[0092] Therefore, with respect to the resonant coupler, since the resonant coupling is highly dependent on the spacing between waveguides 104 and 106, it is important to precisely control the relative position of the coupling portion of waveguides 104 and 106 when the optical switch is in the ON position. This can be achieved by restricting the motion of the MEMS structure to almost vertical motion only, and by including physical restraints such as restraint section 1002 (Figure 10) for restoring the MEMS structure when it is in the ON position.

[0093] Matching the effective refractive indices of the end portion 110 and the intermediate portion 112, and constraining the motion of the MEMS structure, is difficult to achieve. To circumvent this difficulty, in some embodiments, as shown in Figure 18, when the two waveguides 104 and 106 have different refractive indices, at least one of the end portion 110 or the intermediate portion 112 is tapered to facilitate adiabatic coupling between the end portion 110 and the intermediate portion 112 when the optical switch is ON. In the embodiment shown in Figure 18, the end portion 110 of waveguide 106 is tapered to form an adiabatic coupler 1800. The materials and dimensions of the end portion 110 and the intermediate portion 112 should be selected such that the effective refractive index of the induced modes within the adiabatic coupler 1800 is initially less than the effective mode refractive index of the other waveguide 104, and the effective mode refractive index gradually increases to a value that exceeds the effective mode refractive index of the other waveguide 104 in the direction in which the input light propagates. Power is transmitted between the two waveguides 104 and 106 as their individual effective refractive indices intersect.

[0094] Such tapered couplers 1800 are relatively resistant to slight mismatches or displacements of one or both waveguides 104 and 106, manufacturing non-idealisms, material variations between optical switches, etc. On the other hand, manufacturing tolerances must be strictly maintained with respect to the resonant coupler.

[0095] Any of the optical switches described herein may employ either an adiabatic coupler or a resonant coupler, as discussed with respect to Figures 17-18. Furthermore, resonant coupling may provide wavelength selectivity, which may have the potential benefit of background noise reduction or wavelength multiplexing / demultiplexing through a series of optical switches. Photocoupled "frustrator"

[0096] Figure 19 is a perspective view of an optical switch 1900 according to another embodiment of the present invention. Similar to the optical switch 1400 shown in Figures 14 and 15, the two waveguides 104 and 106 are displaced laterally from each other at a distance of 114. However, unlike the optical switch 1400, neither waveguide 104 nor 106 (neither the end portion 110 of one waveguide 106 nor the intermediate portion 112 of the other waveguide) is translated. Instead, the end portion 110 of waveguide 106 and the intermediate portion 112 of the other waveguide 104 are fixed in place relative to the photonic chip 102 such that the intermediate portion 112 is coupled to the end portion 110 with a coupling efficiency of at least 85% at the design wavelength. By keeping both waveguides fixed in place, tighter tolerances regarding the waveguide spacing can be ensured. As described, precisely controlling the relative position of the coupling portion of waveguides 104 and 106 when the optical switch is ON is crucial for highly efficient resonant coupling. In contrast, the prior art optical switch by Seok and Han translates the two couplers, which can lead to matching and spacing problems.

[0097] In the optical switch 1900, the translationable optical component is a film 1902 ("optically coupled frustrator") positioned above the end portion 110 of the waveguide 106. The film 1902 is mechanically coupled to a translationable portion (not shown for clarity) of a MEMS structure 124. Thus, the translationable portion of the MEMS structure 124 translates the film 1902 vertically in a manner similar to how the translationable portion of the MEMS structure 124 translates the end portion 110 of the waveguide 106 in the optical switch 1400, as indicated by the double arrow 1904. The MEMS structure 124 is similar to the MEMS structure 124 described in relation to the optical switch 1400 shown in Figures 14 and 15.

[0098] The material and dimensions of the film 1902 and the distance 1904 over which the film translates are selected such that when the film 1902 is in a first position distal to the end portion 110 ("on" position), the interaction between the film 1902 and the end portion 110 of the waveguide 106 is minimized or negligible, and light couples from the first waveguide 104 to the second waveguide 106 with an efficiency of at least about 85%; however, when the film 1902 is in a second position close to the end portion 110 ("off" position), the film 1902 interacts strongly with the end portion 110. This interaction prevents coupling between the two waveguides 104 and 106 by breaking the symmetry between them. The breaking of symmetry prevents the existence of the symmetric and asymmetric modes described above, and as a result, no coupling occurs between the two waveguides 104 and 106. When the coupling frustrator 1902 is in the off position, the two waveguides 104 and 106 are no longer in phase, and therefore power cannot be coupled between waveguides 104 and 106.

[0099] In the embodiment shown in Figure 19, the coupling frustrator 1902 is positioned only above the end portion 110 of the waveguide 106, whereas in another embodiment shown in Figure 20, in the optical switch 2000, the coupling frustrator 1902 is positioned across the intermediate portion 112 of the other waveguide 104. In yet another embodiment shown in Figure 21, in the optical switch 2100, the coupling frustrator 1902 is positioned to some extent across both the end portion 110 of one waveguide 106 and the intermediate portion 112 of the other waveguide 104.

[0100] As in the optical switch 1900 (Figure 19), positioning the coupling frustrator 1902 only above the end portion 110 of the waveguide 106 has advantages. For example, the light is not coupled very strongly into the coupling frustrator 1902, and the coupling frustrator 1902 may be made from an optically lossy material. If the coupling frustrator 1902 is positioned above the waveguide 104, the coupling frustrator 1902 should be made thin enough so that it does not have inductive modes of its own, and the coupling frustrator 1902 should have low optical loss.

[0101] In another embodiment shown in Figure 22, in the optical switch 2200, the end portion 110 of one waveguide 106 is aligned above the intermediate portion 112 of the other waveguide 104. As in the optical switches 1900, 2000, and 2100, the end portion 110 and the intermediate portion 112 are positioned close enough to couple together without the coupling frustrator 2202. However, unlike the optical switches 1900-2100, in the optical switch 2200, the optical frustrator 2202 is translated perpendicularly along the sides of the two waveguides 104 and 106 (2204). That is, the optical frustrator 2202 is displaced laterally at a distance 114 from the two waveguides 104 and 106, and the optical frustrator 2202 is translated in a plane (not shown) that does not cross the two waveguides 104 and 106.

[0102] In the optical switch embodiments 1900-2200 that translate the optical frustrator 1902 or 2202, the light does not necessarily have to pass through the volume defined by the MEMS structure 124. Therefore, the light does not incident on the material of the MEMS structure 124, except for possible transient interactions. Thus, a material exhibiting certain optical losses can be used for the MEMS structure 124, which is important in that wavelengths around 900 nm are of particular interest in some applications. These wavelengths are absorbed by silicon with absorption lengths similar to those modeled in Figures 23 and 24 (discussed below). Other MEMS devices may not tolerate these optical losses within their individual waveguides. However, as shown in Figures 23 and 24, these optical losses can be tolerated in the MEMS optical frustrator 1902 or 2202, allowing silicon to be used as the material for the MEMS structure 124. This is important because silicon is a preferred material for MEMS devices due to its physical and electrical properties and ease of processing.

[0103] In yet another embodiment of the optical switch (not shown), in which the two waveguides 104 and 106 are arranged either stacked vertically as in Figure 22 or side by side as in Figure 19, the coupling frustrator may be translated laterally rather than vertically in the off state, as long as it is close enough to one of the waveguides to shift the effective refractive index of the waveguide propagation mode relative to the other waveguide. Combined side of the optical switch

[0104] As described herein, the optical switches described herein involve various aspects, including (a) whether the end portion of one waveguide is adjacent to or above the middle portion of another waveguide, (b) whether the end portion is above or below the middle portion, (c) whether the two waveguides are resonantly or adiabatically coupled in the ON state, (d) the number of possible switch states, (e) optical components that translate to change the switch state, and (f) the properties of the translatable optical components. These aspects can be combined in various ways. For example, the optical switch 200 described with reference to Figure 2-4 may include a resonant coupler or an adiabatic coupler. Similarly, the optical switch 400 described with reference to Figure 4-5 may also include a resonant coupler or an adiabatic coupler. Outer boundary of optical switch

[0105] The optical switch 100 has an outer boundary 136 (Figure 1) that defines a minimum defined rectangular area, including a translatable optical component and a MEMS structure 124. The outer boundary 136 is the minimum rectangular area on the photonic chip 102, including the MEMS structure 124 and a translatable optical component, which may be an intermediate portion 112 of the first optical waveguide 104 or an end portion 110 of the second optical waveguide 106. As can be seen in Figure 1, all input / output ports 130-134 are located outside the outer boundary 136. Each end (not shown) of the first optical waveguide 104 is located outside the outer boundary 136. The intermediate portion 112 of the first optical waveguide 104 is located within the outer boundary 136. The first end portion 110 of the second optical waveguide 106 is located within the outer boundary 136. The second end (not shown) of the second optical waveguide 106, opposite the first end portion 110, is located outside the outer boundary 136. The MEMS structure 124 is located within the outer boundary 136. Computer simulation

[0106] Figures 23 and 24 show the results of computer simulations of the optical switch 1900 (Figure 19) performed using the Bidirectional Eigenmode extension and varFDTD engine of Mode Solutions software from Lumerical, Inc. The simulations include an excess bend in the waveguide beyond that shown in Figure 19, for separating the input and output waveguides. Table 1 lists the exemplary device parameters used in the simulations. Figure 23 shows the simulation results of the optical switch 1900 in the ON state, i.e., with the coupled frustrator 1902 distal to the waveguide end portion 110. Figure 24 shows the simulation results of the optical switch 1900 in the OFF state, i.e., with the coupled frustrator 1902 close to the end portion 110. The film material simulated was selected to have significant optical loss (absorption length of approximately 100 microns), and furthermore, the performance of the optical switch 1900 was still excellent. As can be seen from Figures 23 and 24, the optical switch 1900 exhibits low optical loss and excellent attenuation in both states. [Table 1]

[0107] Figures 25 and 26 are perspective views of the optical switch 2500, including an adiabatic coupler 2502 positioned below the intermediate portion 112 of the other waveguide 104. The adiabatic coupler was described with respect to Figure 18. Other aspects of the optical switch 2500 are similar to other embodiments described herein with respect to Figures 4, 5, 10, 11, and 18, etc. Figures 25 and 26 illustrate the translationable portion of the MEMS structure 124 as a wireframe. Figure 25 illustrates the MEMS structure 124 when the optical switch 2500 is in the off state, i.e., the intermediate portion 112 is distal to the adiabatic coupler 2502, and Figure 26 illustrates the MEMS structure 124 when the optical switch 2500 is in the on state, i.e., the intermediate portion 112 is close to the adiabatic coupler 2502. Arrow 2504 indicates the path of light propagation from waveguide 104 to waveguide 106 through optical switch 2500.

[0108] Figures 27, 28, 29, and 30 show the computer simulation results for the optical switch 2500. Table 2 lists the exemplary device parameters used in the simulation. [Table 2]

[0109] Figures 27 and 29 depict graphs of the optical power (mode profile) at various x and y coordinates within the cross-section of the optical switch 2500, as viewed from the cross-sectional plane 2506, when the optical switch 2500 is in the off and on states, respectively, i.e., at the starting point of the adiabatic coupler 2502 (in the direction of light propagation). Figures 28 and 30 depict graphs of the optical power (mode profile) at various x and y coordinates within the cross-section of the optical switch 2500, as viewed from the cross-sectional plane 2508, when the optical switch 2500 is in the off and on states, respectively, i.e., at the ends of the adiabatic coupler 2502 (in the direction of light propagation).

[0110] In Figures 27-30, position 2700 represents the bus waveguide 104, and position 2702 represents the other waveguide 106. When the optical switch 2500 is in the off state, the propagation mode remains confined to the upper bus waveguide 104 (position 2700), as can be seen in Figures 27 and 28; that is, no light is coupled to the adiabatic coupler 2502. However, when the optical switch 2500 is in the on state, the propagation mode may be seen in the bus waveguide 104 at position x, which corresponds to the starting point of the adiabatic coupler 2502 (Figure 29), but the propagation mode is coupled from the bus waveguide 104 to the bottom waveguide 106 (Figure 30), with the majority of the power confined to the bottom waveguide 106, by position x, which corresponds to the ending point of the adiabatic coupler 2502.

[0111] Dimensions for one implementation of the optical switch 2500 using silicon nitride for waveguides 104 and 106 are provided in Table 2. The overall length and waveguide dimensions of the optical switch 2500 can be adjusted according to the desired total size and required performance of the optical switch 2500. Other materials, such as silicon, sapphire, titanium dioxide, diamond, silicon carbide, and chalcogenide glass, can also be used for the waveguides, depending on the operation and desired wavelength of optical power to be addressed by the optical switch 2500. Additional / alternative structures and / or materials

[0112] Figure 31 is a partial top view of a MEMS structure 124 for translating a waveguide or coupled frustrator according to one embodiment of the present invention, Figure 32 is a side view thereof (optical switch in the off state), Figure 33 is a side view thereof (optical switch in the on state), and Figure 34 is a cross-sectional view thereof. The thickness dimensions in Figure 34 (approximately 100 nm and approximately 300 nm, respectively) are examples of dimensions that contain silicon-rich silicon nitride material and work well for embodiments operating at a wavelength of approximately 1,550 nm. However, in other embodiments, the thickness, waveguide material, and wavelength may vary depending on the design choice. The distance 3300 (Figure 33) is approximately 100 μm or longer in some embodiments to accommodate the tension in the operating region. The MEMS structure 124 is mainly applicable to optical switches in which two waveguides 104 and 106 are arranged overlapping one above the other. Ideally, the waveguide material, which is likely to be an electrical insulator, is deposited on top of the MEMS structural material and on top of the electrodes. Alternatively, the MEMS structural material may be deposited on top of the waveguide material. However, this would result in an electrical insulator between the upper and lower electrodes.

[0113] Figure 35 is a top view of a portion of a MEMS structure 124 for translating a waveguide or coupled frustrator according to another embodiment of the present invention, and Figure 36 is a cross-sectional view thereof. The thin slab between the waveguide and the pad for operation shown in Figure 35 is optional. Figure 36 shows the upper waveguide directly above the lower waveguide, although the lower waveguide does not need to be directly below the upper waveguide. The thickness dimensions in Figure 34 (about 100 nm and about 300 nm, respectively) are examples of dimensions that work well for embodiments containing silicon-rich silicon nitride material and operating at a wavelength of about 1,550 nm. However, in other embodiments, the thickness, waveguide material, and wavelength may vary depending on the design choice. Side views of the switch-off and switch-on states are similar to Figures 32 and 33. The MEMS structure 124 is primarily applicable to optical switches in embodiments such as those shown in Figures 14, 15, and 22, where a portion of the waveguide or coupling frustrator is translated perpendicularly along the side of one or more other waveguides, and the translating upper layer can be anchored to only one side.

[0114] In a state where the operation occurs on only one side, as shown in Figures 35-36, a stopper may be used to prevent contact between the upper and lower waveguides. Otherwise, a single electrode pair would likely result in a tilted upper waveguide, in contrast to a single electrode pair on both sides of the waveguide, when the MEMS structure is operated. The stopper flattens the working portion of the MEMS structure.

[0115] Figures 37 and 38 are side views of a MEMS structure 124 in separate off and on states according to another embodiment of the present invention. In this embodiment, a piezoelectric material is used for operation, rather than a pair of electrodes that electrostatically attract or repel each other. This piezoelectric material expands or contracts in response to an operating voltage applied to the upper conductor. This expansion or contraction results in the bending of the MEMS structure as shown in Figure 38. The lower stop limits the translation of the MEMS structure and therefore flattens the MEMS structure to the right.

[0116] Figure 39 is a top view of an ON state MEMS structure 124 according to another embodiment of the present invention. This MEMS structure 124 may be used, for example, to translate a coupled frustrator. The upper part 3900 of the MEMS structure 124 is shown schematicly only to expose the lower components of the upper part, including the end portion 110 of the waveguide 106. Arrow 3902 indicates the path taken by the light as it couples from waveguide 104 to waveguide 106. The upper part 3900 may be perforated to allow air to flow through the perforations as the upper part translates, thereby reducing friction with the air.

[0117] The waveguides and / or MEMS structures described herein may, as an alternative, be fabricated from aluminum nitride, depending on the design wavelength of the optical switch. Alternatively, the MEMS structures described herein may be fabricated from scandium aluminum nitride or various metals.

[0118] The present invention is described through the exemplary embodiments described above, but modifications and variations of the illustrated embodiments can be made without departing from the concept of the invention disclosed herein. For example, specific parameter values ​​such as dimensions and materials can be listed in relation to embodiments disclosed within the scope of the invention, but the values ​​of all parameters can vary over a wide range to suit different applications. Unless otherwise indicated in the context or understood otherwise by a person skilled in the art, terms such as “about” mean within ±20%.

[0119] As used herein, including in the claims, the term "and / or" as used in relation to the enumeration of items means one or more of the items in the enumeration, i.e., at least one of the items in the enumeration, and not necessarily all of the items in the enumeration. As used herein, including in the claims, the term "or" as used in relation to the enumeration of items means one or more of the items in the enumeration, i.e., at least one of the items in the enumeration, and not necessarily all of the items in the enumeration. Unless otherwise indicated, "or" does not mean "exclusively or".

[0120] The disclosed aspects or any part thereof may be combined in ways not listed above and / or expressly claimed. In addition, the embodiments disclosed herein can be adequately practiced without any elements not specifically disclosed herein. Therefore, the present invention should not be considered limited to the disclosed embodiments.

Claims

1. 1. An optical switch having a design wavelength, the optical switch comprising: A photonic chip, a translatable optical coupling frustrated element; a first optical waveguide disposed on the photonic chip, the first optical waveguide having an intermediate portion; a second optical waveguide distinct from the first optical waveguide, the second optical waveguide disposed on the photonic chip and having a first end portion, the first end portion being stationary with respect to an intermediate portion of the first optical waveguide, the first end portion being sufficiently close to an intermediate portion of the first optical waveguide such that the first end portion evanescently couples with the intermediate portion of the first optical waveguide in the absence of the optical coupling frustration, and a coupling efficiency between the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide is at least about 85% at the design wavelength; a MEMS structure disposed on the photonic chip, the MEMS structure having a translatable portion mechanically coupled to the optical coupling frustrator, the translatable portion configured to translate the optical coupling frustrator in response to a control signal between at least (a) a first position proximate to at least one of the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide, and (b) a second position spaced apart from the at least one of the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide; Equipped with in the first position, the optical coupling frustrator is sufficiently proximate to at least one of the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide to prevent evanescent coupling between the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide, and a coupling efficiency between the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide is less than about 10% at the design wavelength; an optical switch, wherein in the second position, the optical coupling frustration is sufficiently spaced from at least one of the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide to enable evanescent coupling between the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide, and a coupling efficiency between the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide is at least about 85% at the design wavelength.

2. 2. The optical switch of claim 1, wherein in both the first and second positions, the optical coupling frustration is aligned above at least a portion of at least one of the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide when viewed normal to the photonic chip.

3. 2. The optical switch of claim 1, wherein in both the first and second positions, the optical coupling frustration is laterally displaced from the intermediate portion of the first optical waveguide and the first end portion of the second optical waveguide when viewed normal to the photonic chip.

4. 2. The optical switch of claim 1, wherein in the first position, the optical coupling frustration is proximate to the intermediate portion of the first optical waveguide, and in the second position, the optical coupling frustration is spaced from the intermediate portion of the first optical waveguide.

5. 2. The optical switch of claim 1, wherein in the first position, the optical coupling frustration is proximate to the first end portion of the second optical waveguide, and in the second position, the optical coupling frustration is spaced from the first end portion of the second optical waveguide.

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