CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims the benefit of U.S. Provisional Patent Application No. 63/171,381, filed April 6, 2021 by Hongzhen Wei, et al., and titled “Large Mode Size Edge Coupling With SiN Dual Taper Bridge,” which application is hereby incorporated by reference.

TECHNICAL FIELD

[0002] The present disclosure is generally related to Silicon (Si) based optical network communications, and is specifically related to an optical coupler to support coupling optical signals from a Si waveguide to an optical fiber.

BACKGROUND

[0003] Si based photonics uses silicon as an optical medium. Si based photonics leverages the fact that most computational devices are implemented in Si. Accordingly, Si photonics allows optical components to be integrated into the same package as computational components. This can result in significant miniaturization of the final package. The package can then be coupled to a fiber for communication over an optical communications network. One of the issues with Si photonics is that the Si components are much smaller than the fiber. As such, couplers are used to couple the light from the smaller Si components to the larger fiber. An optical signal propagates through a medium in a mode. The mode size of the Si components is generally different than the mode size in the fiber because of the refractive index contrast difference between the component core layer and the fiber cladding layer. A coupler is designed to enhance fiber to silicon photonics device coupling efficiency and improve alignment tolerance. A coupler should also minimize the amount of light lost between the Si components and the fiber during the coupling process. Some couplers use a lens to couple the light toward the fiber. The problem with lenses is that the alignment tolerance is very small when used with the current Si components employed in modem Si photonics. Since the alignment tolerance is small, the alignment tolerance is not supported by 2.5 dimension (2.5D) and 3 dimension (3D) silicon photonics device packages because these device packages are exposed to a high temperature processing after an optical fiber is attached to the devices. For example, the lenses may be applied to precise locations via an adhesive. However, a combination of heat and vibration during the manufacturing process can cause the lenses to shift in an uncontrolled manner. As such, the resulting devices of a current silicon coupler may vary significantly in the amount of light lost and the contiguously usable modes across a manufactured batch.

SUMMARY

[0004] In an embodiment, the disclosure includes an optical coupler comprising: a silicon on insulator (SOI) wafer; a silicon waveguide including a channel and a waveguide inverse taper; a bridge disposed above the waveguide inverse taper; a dielectric ridge disposed above the bridge; and a silicon dioxide layer disposed above dielectric ridge waveguide.

[0005] In order to avoid the issues associated with lenses as detailed above, an example optical coupler employs a dielectric ridge suspended above a Si waveguide. The dielectric ridge can be designed to provide modes that match the modes of the corresponding optical fiber. Further, the Si waveguide employs an inverse taper, which can adiabatically couple light between the waveguide and silicon nitride (SiN) bridge waveguide and between the SiN bridge waveguide and the silicon oxide nitride (SiON) dielectric ridge waveguide. For example, the inverse taper reduces return loss when the light couples from the waveguide to the dielectric ridge with a smaller silicon reverse taper tip size such as less than 100 nanometers (nm). Return loss is light lost when the light reflects back at an interface instead of proceeding through the interface. One concern with this design is that the amount of light lost, both due to return loss and loss of optical energy transferring from bridge waveguide mode to silicon channel waveguide mode, is related to the narrowness of the tip of the inverse taper. Another concern is the design of reverse silicon taper and bridge silicon nitride taper profile for minimizing optical energy transferring loss from the bridge waveguide to the reverse silicon waveguide in the optical coupler.

[0006] The present embodiment includes an optical coupler design that allows for the constraints of the inverse taper to be relaxed to a level that can be supported by the precision of current manufacturing technologies. Specifically, the present disclosure includes a bridge disposed between the Si waveguide and the dielectric ridge. In an example, the Si waveguide includes a channel waveguide with an inverse taper above a silicon dioxide box layer of a Silicon on Insulator (SOI) wafer. The bridge is disposed above the silicon waveguide inverse taper. The bridge may include both a bridge taper and a bridge inverse taper. The bridge taper may extend above an interface between the channel waveguide and the inverse taper waveguide. The bridge may be formed of Silicon Nitride (SiN). The bridge may also be separated from the waveguide by a gap that includes at least one layer of dielectric on the SOI surface with a silicon substrate. The dielectric ridge may then extend above the bridge waveguide. For example, the dielectric ridge may include a ridge taper, a facet, and an interface between the ridge taper and the facet. In some examples, the bridge inverse taper extends below the interface between the ridge taper and the facet. In some examples, the bridge inverse taper extends below the dielectric ridge waveguide all the way to the facet. The dielectric ridge waveguide may be composed of Silicon Oxynitride (SiON). Further, a silicon dioxide (Si02) layer may cover on the top of dielectric ridge waveguide. In an example, a partial etch may be applied to the tip of the inverse taper to further reduce light confinement in the tip of silicon waveguide and reduce return loss. By using this structure, light first adiabatically couples between the inverse taper of the waveguide and the taper of the bridge. The light then adiabatically couples between the bridge inverse taper and the ridge taper of the dielectric ridge. This dual adiabatic process pseudo-continuously minimizes the discontinuities and supports mode matching and optical energy transferring from one waveguide to another. The silicon and SiN reverse taper can be linear tapering or nonlinear tapering to make the optical coupler size compact. The light can then couple between the dielectric ridge waveguide and the fiber with low optical loss. The bridge includes an index contrast and dimension that is similar to that of the Si waveguide, which allows the tip width constraints related to the waveguide inverse taper to be relaxed. This design also supports both transverse electric (TE) modes and transverse magnetic (TM) modes with low optical loss. Accordingly, the present disclosure includes an optical coupler design that supports the relaxation of constraints while maintaining beneficial optical containment and reduced loss of optical signal power. Further, the disclosed silicon optical coupler to optical fiber coupling can tolerate unavoidable shifts of fiber to silicon chip for 2.5D and 3D high temperature reflow and other fabrication processing.

[0007] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the bridge comprising a bridge taper disposed over the waveguide inverse taper.

[0008] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the bridge comprising Silicon Nitride (SiN).

[0009] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the bridge separated from the silicon waveguide by a gap filled with silicon dioxide. [0010] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the silicon waveguide comprising an inverse taper interface between the channel and the waveguide inverse taper, and the bridge taper extending above the inverse taper interface. [0011] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the dielectric ridge extending above the inverse taper interface. [0012] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the dielectric ridge extending between the inverse taper interface and a termination of the waveguide inverse taper.

[0013] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the bridge comprising a bridge inverse taper disposed below the dielectric ridge.

[0014] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the dielectric ridge comprising a ridge taper and a facet, the bridge inverse taper extending to the facet.

[0015] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the dielectric ridge comprising a ridge taper, a facet, and a ridge interface between the ridge taper and the facet, the bridge inverse taper extending to the ridge interface.

[0016] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the dielectric ridge comprising Silicon Oxynitride (SiON).

[0017] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the waveguide inverse taper including a tip with a partial etch.

[0018] In an embodiment, the disclosure includes a method of manufacturing an optical coupler, the method comprising: fabricating a silicon waveguide on top of a silicon on insulator (SOI) wafer, the silicon waveguide including a channel and terminating in a waveguide inverse taper; depositing a bridge above the waveguide inverse taper; and depositing a dielectric ridge disposed above the bridge.

[0019] In order to avoid the issues associated with lenses as detailed above, an example optical coupler employs a dielectric ridge suspended above a Si waveguide. The dielectric ridge can be designed to provide modes that match the modes of the corresponding optical fiber. Further, the Si waveguide employs an inverse taper, which can adiabatically couple light between the waveguide and silicon nitride (SiN) bridge waveguide and between the SiN bridge waveguide and the silicon oxide nitride (SiON) dielectric ridge waveguide. For example, the inverse taper reduces return loss when the light couples from the waveguide to the dielectric ridge with a smaller silicon reverse taper tip size such as less than 100 nanometers (nm). Return loss is light lost when the light reflects back at an interface instead of proceeding through the interface. One concern with this design is that the amount of light lost, both due to return loss and loss of optical energy transferring from bridge waveguide mode to silicon channel waveguide mode, is related to the narrowness of the tip of the inverse taper. Another concern is the design of reverse silicon taper and bridge silicon nitride taper profile for minimizing optical energy transferring loss from the bridge waveguide to the reverse silicon waveguide in the optical coupler. [0020] The present embodiment includes an optical coupler design that allows for the constraints of the inverse taper to be relaxed to a level that can be supported by the precision of current manufacturing technologies. Specifically, the present disclosure includes a bridge disposed between the Si waveguide and the dielectric ridge. In an example, the Si waveguide includes a channel waveguide with an inverse taper above a silicon dioxide box layer of a Silicon on Insulator (SOI) wafer. The bridge is disposed above the silicon waveguide inverse taper. The bridge may include both a bridge taper and a bridge inverse taper. The bridge taper may extend above an interface between the channel waveguide and the inverse taper waveguide. The bridge may be formed of Silicon Nitride (SiN). The bridge may also be separated from the waveguide by a gap that includes at least one layer of dielectric on the SOI surface with a silicon substrate. The dielectric ridge may then extend above the bridge waveguide. For example, the dielectric ridge may include a ridge taper, a facet, and an interface between the ridge taper and the facet. In some examples, the bridge inverse taper extends below the interface between the ridge taper and the facet. In some examples, the bridge inverse taper extends below the dielectric ridge waveguide all the way to the facet. The dielectric ridge waveguide may be composed of Silicon Oxynitride (SiON). Further, a silicon dioxide (Si02) layer may cover on the top of dielectric ridge waveguide. In an example, a partial etch may be applied to the tip of the inverse taper to further reduce light confinement in the tip of silicon waveguide and reduce return loss. By using this structure, light first adiabatically couples between the inverse taper of the waveguide and the taper of the bridge. The light then adiabatically couples between the bridge inverse taper and the ridge taper of the dielectric ridge. This dual adiabatic process pseudo-continuously minimizes the discontinuities and supports mode matching and optical energy transferring from one waveguide to another. The silicon and SiN reverse taper can be linear tapering or nonlinear tapering to make the optical coupler size compact. The light can then couple between the dielectric ridge waveguide and the fiber with low optical loss. The bridge includes an index contrast and dimension that is similar to that of the Si waveguide, which allows the tip width constraints related to the waveguide inverse taper to be relaxed. This design also supports both transverse electric (TE) modes and transverse magnetic (TM) modes with low optical loss. Accordingly, the present disclosure includes an optical coupler design that supports the relaxation of constraints while maintaining beneficial optical containment and reduced loss of optical signal power. Further, the disclosed silicon optical coupler to optical fiber coupling can tolerate unavoidable shifts of fiber to silicon chip for 2.5D and 3D high temperature reflow and other fabrication processing. [0021] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the bridge comprising a bridge taper deposited over the waveguide inverse taper. [0022] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the bridge comprising Silicon Nitride (SiN).

[0023] Optionally, in any of the preceding aspects, another implementation of the aspect provides, further comprising depositing a silicon dioxide (Si02) layer of insulator between the bridge and the silicon waveguide.

[0024] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the silicon waveguide comprising an inverse taper interface between the channel and the waveguide inverse taper, and the bridge taper deposited to extend above the inverse taper interface.

[0025] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the dielectric ridge deposited to extend above the inverse taper interface.

[0026] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the dielectric ridge deposited to extend between the inverse taper interface and a termination of the waveguide inverse taper.

[0027] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the bridge comprising a bridge inverse taper deposited to extend below the dielectric ridge.

[0028] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the dielectric ridge comprising a ridge taper and a facet, the bridge inverse taper deposited to extend to the facet.

[0029] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the dielectric ridge comprising a ridge taper, a facet, and a ridge interface between the ridge taper and the facet, the bridge inverse taper deposited to extend to the ridge interface. [0030] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the dielectric ridge comprising Silicon Oxynitride (SiON).

[0031] Optionally, in any of the preceding aspects, another implementation of the aspect provides, further comprising performing a partial etch of a tip of the waveguide inverse taper. [0032] In an embodiment, the disclosure includes a manufacturing device for manufacturing an optical coupler, the means comprising: a fabricating means for fabricating a silicon waveguide on top of a silicon on insulator (SOI) wafer, the silicon waveguide including a channel and terminating in a waveguide inverse taper; a first depositing means for depositing a bridge above the waveguide inverse taper; and a second depositing means for depositing a dielectric ridge disposed above the bridge.

[0033] In order to avoid the issues associated with lenses as detailed above, an example optical coupler employs a dielectric ridge suspended above a Si waveguide. The dielectric ridge can be designed to provide modes that match the modes of the corresponding optical fiber. Further, the Si waveguide employs an inverse taper, which can adiabatically couple light between the waveguide and silicon nitride (SiN) bridge waveguide and between the SiN bridge waveguide and the silicon oxide nitride (SiON) dielectric ridge waveguide. For example, the inverse taper reduces return loss when the light couples from the waveguide to the dielectric ridge with a smaller silicon reverse taper tip size such as less than 100 nanometers (nm). Return loss is light lost when the light reflects back at an interface instead of proceeding through the interface. One concern with this design is that the amount of light lost, both due to return loss and loss of optical energy transferring from bridge waveguide mode to silicon channel waveguide mode, is related to the narrowness of the tip of the inverse taper. Another concern is the design of reverse silicon taper and bridge silicon nitride taper profile for minimizing optical energy transferring loss from the bridge waveguide to the reverse silicon waveguide in the optical coupler.

[0034] The present embodiment includes an optical coupler design that allows for the constraints of the inverse taper to be relaxed to a level that can be supported by the precision of current manufacturing technologies. Specifically, the present disclosure includes a bridge disposed between the Si waveguide and the dielectric ridge. In an example, the Si waveguide includes a channel waveguide with an inverse taper above a silicon dioxide box layer of a Silicon on Insulator (SOI) wafer. The bridge is disposed above the silicon waveguide inverse taper. The bridge may include both a bridge taper and a bridge inverse taper. The bridge taper may extend above an interface between the channel waveguide and the inverse taper waveguide. The bridge may be formed of Silicon Nitride (SiN). The bridge may also be separated from the waveguide by a gap that includes at least one layer of dielectric on the SOI surface with a silicon substrate. The dielectric ridge may then extend above the bridge waveguide. For example, the dielectric ridge may include a ridge taper, a facet, and an interface between the ridge taper and the facet. In some examples, the bridge inverse taper extends below the interface between the ridge taper and the facet. In some examples, the bridge inverse taper extends below the dielectric ridge waveguide all the way to the facet. The dielectric ridge waveguide may be composed of Silicon Oxynitride (SiON). Further, a silicon dioxide (Si02) layer may cover on the top of dielectric ridge waveguide. In an example, a partial etch may be applied to the tip of the inverse taper to further reduce light confinement in the tip of silicon waveguide and reduce return loss. By using this structure, light first adiabatically couples between the inverse taper of the waveguide and the taper of the bridge. The light then adiabatically couples between the bridge inverse taper and the ridge taper of the dielectric ridge. This dual adiabatic process pseudo-continuously minimizes the discontinuities and supports mode matching and optical energy transferring from one waveguide to another. The silicon and SiN reverse taper can be linear tapering or nonlinear tapering to make the optical coupler size compact. The light can then couple between the dielectric ridge waveguide and the fiber with low optical loss. The bridge includes an index contrast and dimension that is similar to that of the Si waveguide, which allows the tip width constraints related to the waveguide inverse taper to be relaxed. This design also supports both transverse electric (TE) modes and transverse magnetic (TM) modes with low optical loss. Accordingly, the present disclosure includes an optical coupler design that supports the relaxation of constraints while maintaining beneficial optical containment and reduced loss of optical signal power. Further, the disclosed silicon optical coupler to optical fiber coupling can tolerate unavoidable shifts of fiber to silicon chip for 2.5D and 3D high temperature reflow and other fabrication processing.

[0035] Optionally, in any of the preceding aspects, another implementation of the aspect provides, the device being further configured to perform the method of any of the preceding aspects.

[0036] For the purpose of clarity, any one of the foregoing embodiments may be combined with any one or more of the other foregoing embodiments to create a new embodiment within the scope of the present disclosure.

[0037] These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

[0039] FIG. 1 A is atop view of an example optical coupler.

[0040] FIGS. 1B-1E are cross sectional views ofthe example optical coupler at cross sections B-E, respectively.

[0041] FIG. 2 A is a top view of an example optical coupler including a waveguide inverse taper with an etched tip. [0042] FIGS. 2B-2D are cross sectional views of the example optical coupler with the etched tip at cross sections B-D, respectively.

[0043] FIG. 3 is a top view of an example optical coupler with a dielectric ridge including a ridge interface and a bridge that extends below the ridge interface.

[0044] FIG. 4 is a top view of an example optical coupler with a dielectric ridge including a facet and a bridge that extends below the facet.

[0045] FIG. 5 is a graph of return loss at optical interface one for example optical couplers with varying insulator gap sizes between the waveguide and the bridge.

[0046] FIG. 6 is a graph of the effective index for various waveguide and bridge widths of an example optical coupler.

[0047] FIG. 7 is a graph of the coupling loss at optical interface two at various wavelengths for an example optical coupler.

[0048] FIG. 8 is a graph of the return loss at optical interface two at various wavelengths for an example optical coupler.

[0049] FIG. 9 is a graph of the coupling loss related to an etched tip of a waveguide inverse taper at various wavelengths for an example optical coupler.

[0050] FIG. 10 is a graph of the return loss related to an etched tip of a waveguide inverse taper at various wavelengths for an example optical coupler.

[0051] FIG. 11 is a graph of the coupling loss between the waveguide and the bridge at various wavelengths for an example optical coupler.

[0052] FIG. 12 is a graph of the coupling loss related to the tip of the inverse taper of the bridge at various wavelengths for an example optical coupler.

[0053] FIG. 13 is a graph of the return loss related to the tip of the inverse taper of the bridge at various wavelengths for an example optical coupler.

[0054] FIG. 14 is a graph of the bridge and dielectric ridge confinement at various bridge widths and wavelengths for an example optical coupler.

[0055] FIG. 15 is a graph of the coupling loss between the bridge and the dielectric ridge at various wavelengths for an example optical coupler.

[0056] FIG. 16 is a schematic diagram of an example control device for designing/manufacturing an optical coupler.

[0057] FIG. 17 is a flowchart of an example method of manufacturing an optical coupler.

[0058] FIG. 18 is an example of a manufacturing device for manufacturing an optical coupler. DETAILED DESCRIPTION

[0059] It should be understood at the outset that although an illustrative implementation of one or more embodiments are provided below, the disclosed systems and/or methods may be implemented using any number of techniques, whether currently known or yet to be developed. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents.

[0060] In order to avoid the issues associated with lenses as detailed above, an example optical coupler employs a dielectric ridge suspended above a Si waveguide. The dielectric ridge can be designed to provide modes that match the modes of the corresponding optical fiber. Further, the Si waveguide employs an inverse taper, which can adiabatically couple light between the waveguide and silicon nitride (SiN) bridge waveguide and between the SiN bridge waveguide and the silicon oxide nitride (SiON) dielectric ridge waveguide. For example, the inverse taper reduces return loss when the light couples from the waveguide to the dielectric ridge with a smaller silicon reverse taper tip size such as less than 100 nanometers (nm). Return loss is light lost when the light reflects back at an interface instead of proceeding through the interface. One concern with this design is that the amount of light lost, both due to return loss and loss of optical energy transferring from bridge waveguide mode to silicon channel waveguide mode, is related to the narrowness of the tip of the inverse taper. Another concern is the design of reverse silicon taper and bridge silicon nitride taper profile for minimizing optical energy transferring loss from the bridge waveguide to the reverse silicon waveguide in the optical coupler.

[0061] Disclosed herein is an optical coupler design that allows for the constraints of the inverse taper to be relaxed to a level that can be supported by the precision of current manufacturing technologies. Specifically, the present disclosure includes a bridge disposed between the Si waveguide and the dielectric ridge. In an example, the Si waveguide includes a channel waveguide with an inverse taper above a silicon dioxide box layer of a Silicon on Insulator (SOI) wafer. The bridge is disposed above the silicon waveguide inverse taper. The bridge may include both a bridge taper and a bridge inverse taper. The bridge taper may extend above an interface between the channel waveguide and the inverse taper waveguide. The bridge may be formed of Silicon Nitride (SiN). The bridge may also be separated from the waveguide by a gap that includes at least one layer of dielectric on the SOI surface with a silicon substrate. The dielectric ridge may then extend above the bridge waveguide. For example, the dielectric ridge may include a ridge taper, a facet, and an interface between the ridge taper and the facet. In some examples, the bridge inverse taper extends below the interface between the ridge taper and the facet. In some examples, the bridge inverse taper extends below the dielectric ridge waveguide all the way to the facet. The dielectric ridge waveguide may be composed of Silicon Oxynitride (SiON). Further, a silicon dioxide (S1O2) layer may cover on the top of dielectric ridge waveguide. In an example, a partial etch may be applied to the tip of the inverse taper to further reduce light confinement in the tip of silicon waveguide and reduce return loss. By using this structure, light first adiabatically couples between the inverse taper of the waveguide and the taper of the bridge. The light then adiabatically couples between the bridge inverse taper and the ridge taper of the dielectric ridge. This dual adiabatic process pseudo-continuously minimizes the discontinuities and supports mode matching and optical energy transferring from one waveguide to another. The silicon and SiN reverse taper can be linear tapering or nonlinear tapering to make the optical coupler size compact. The light can then couple between the dielectric ridge waveguide and the fiber with low optical loss. The bridge includes an index contrast and dimension that is similar to that of the Si waveguide, which allows the tip width constraints related to the waveguide inverse taper to be relaxed. This design also supports both transverse electric (TE) modes and transverse magnetic (TM) modes with low optical loss. Accordingly, the present disclosure includes an optical coupler design that supports the relaxation of constraints while maintaining beneficial optical containment and reduced loss of optical signal power. Further, the disclosed silicon optical coupler to optical fiber coupling can tolerate unavoidable shifts of fiber to silicon chip for 2.5D and 3D high temperature reflow and other fabrication processing.

[0062] FIG. 1A is a top view of an example optical coupler 100. The optical coupler 100 comprises a waveguide 103, a bridge 105, and a dielectric ridge 110. It should be noted that the waveguide 103, the bridge 105, and the dielectric ridge 110 are all waveguides, but the word waveguide has been omitted from the bridge 105 and the dielectric ridge 110 to support clarity of discussion. In the example shown, the waveguide 103 comprises Si, which is depicted with vertical hashing. Further, the bridge 105 may comprise SiN, which is depicted with horizontal hashing. The dielectric ridge 110 may comprise SiON, which is shown as an outlined shape without hashing. The dielectric ridge 110 may also comprise any dielectric material with a refractive index higher than S1O2, for example a refractive index of 1.48 to 1.6 at 1.55um wavelength. The components of the optical coupler 100 may be created by a silicon photonics fabrication foundry based on silicon on insulator (SOI) technology as shown in FIGs 1B-1E. Specifically, a SOI wafer comprises a S1O2 box layer 117 disposed on a Si substrate layer 121. The optical coupler 100 is printed onto the SOI wafer. For example, a Si layer 120 can be deposited onto the S1O2 box layer 117. The Si layer 120 comprises a Si waveguide 103 including a channel 101 and a waveguide inverse taper 102. In a specific example, the channel 101 and the waveguide inverse taper 102 can be formed on a top silicon layer as part of a 220 nm SOI process by employing dry etching. Then, a S1O2 gap layer is deposited onto the functional Si layer 120 to create an insulator gap 116. Next, a SiN layer including the bridge 105 is deposited onto the S1O2 gap layer after etching the bridge 105. Next, a SiON layer (e.g., six micrometers (pm) thickness) is deposited. Then, the dielectric ridge 110 is fabricated from the SiON layer before depositing a S1O2 covering layer. Accordingly, the areas without components include an insulator 115, which is depicted as open space to support visual clarity. The insulator 115 may comprise S1O2.

[0063] The channel 101 is coupled to other components and is configured to propagate optical signals. For example, the channel 101 may be coupled to silicon photonics devices, such as silicon Mach-Zehnder modulators, lasers, and/or receivers (not shown). The light may traverse optical modulators configured to modulate the light to create a signal. Accordingly, the optical signal is received at the channel 101. The optical coupler 100 is designed to couple the light (in the form of an optical signal) from the channel 101 into a fiber connected at a facet 112 of the dielectric ridge 110. Hence, the channel 101 of the waveguide 103 terminates in the waveguide inverse taper 102, which supports transitioning the light out of the waveguide 103. Return loss describes the scenario where light reflects back toward the source and is therefore lost instead of proceeding toward the light’s intended destination. The waveguide inverse taper 102 forwards the light upward toward the bridge 105, while mitigating return loss.

[0064] The optical coupler 100 also includes the bridge 105 disposed above the waveguide inverse taper 102. For example, the bridge 105 may include a bridge taper 106 and a bridge inverse taper 107. The bridge taper 106 is disposed above the waveguide inverse taper 102, and hence the bridge taper 106 attracts light coupled from the waveguide inverse taper 102 of the waveguide 103. The light then flows through the bridge 105 from the bridge taper 106. The bridge inverse taper 107 is disposed below the dielectric ridge 110. The bridge inverse taper 107 operates in a similar manner to the waveguide inverse taper 102. The bridge inverse taper 107 transfers optical energy to a dielectric ridge 110, which aligns the output mode size to a mode size similar to a fiber mode size at facet 112 of optical coupler 100.

[0065] The optical coupler 100 also includes the dielectric ridge 110 disposed directly above the bridge 105 and disposed over at least portions of the waveguide 103. The dielectric ridge 110 includes a ridge taper 111 and a facet 112. The ridge taper 111 of the dielectric ridge 110 is at least disposed above bridge inverse taper 107. Hence, the ridge taper 111 acts as a bridge waveguide cladding layer, and at these sections, optical energy is confined in the silicon waveguide 103 and the SiN bridge 105. At the optical interface 2, optical energy is confined in the SiN bridge 105. From interface 2 to interface 3, optical energy is adiabatically and gradually transferred into the SiON dielectric ridge 110. At the interface 3, optical energy is transferred into dielectric ridge 110 completely. In the example shown, the ridge taper 111 is also disposed above the bridge taper 106 and hence also disposed above the waveguide inverse taper 102. For example, the ridge taper 111 (and/or the dielectric ridge 110) may extend above the inverse taper interface between the channel 101 and the waveguide inverse taper 102. The bridge taper 106 may also extend above the inverse taper interface between the channel 101 and the waveguide inverse taper 102. In some examples, the ridge taper 111 (and/or the dielectric ridge 110) may extend to any position between the inverse taper interface of the waveguide 103 and a termination (tip) of the waveguide inverse taper 102. In some examples, the dielectric ridge 110 is not tapered. In such a case, the dielectric ridge 110 is rectangular. The facet 112 is a connection point for the fiber. Hence, the dielectric ridge 110/ ridge taper 111 channels light from the waveguide 103 and the bridge 105 toward the facet 112 for coupling onto the fiber. Also, since the dielectric ridge 110 is configured to couple light onto the fiber, the relative width, length, shape, and position of the dielectric ridge 110 can be modified to tune the available modes (e.g., mode size) at the facet 112 to match the available modes of atarget fiber. It should be noted that light is described as moving from the channel 101 toward the facet 112 for simplicity of discussion. However, the optical coupler 100 is bidirectional, and hence light can also be received at the facet 112 and forwarded toward the channel 101 for receipt at a Si photonics receiver.

[0066] The optical coupler 100 includes various interfaces where light transitions between components. For example, the optical coupler 100 includes a first optical interface (Optical Interface 1) between the channel 101 and the bridge taper 106/ ridge taper 111. The optical coupler 100 also includes a second optical interface (Optical Interface 2) at the termination/tip of the waveguide inverse taper 102. The optical coupler 100 also includes a third optical interface (Optical Interface 3) at the termination/tip of the bridge inverse taper 107. These optical interfaces are the locations that cause return loss and/or loss of confinement. Accordingly, the widths and shapes of the relevant components at Optical Interface 1, Optical Interface 2, and Optical Interface 3 can be tuned to alter optical loss. For example, the optical loss may be related to the cross-sectional dimensions of the relevant components at the corresponding optical interface. In general, small er/narrower tip widths for both the waveguide inverse taper 102 and the bridge inverse taper 107 reduce interruption on light propagation, and hence reduce optical loss. The narrowness of the tip widths may be limited by manufacturing process capability. In an example, the waveguide inverse taper 102 has a tip width 0.13 micrometers (pm) at the smallest point. In an example, the bridge inverse taper 107 has a tip width of 0.2 pm at the smallest point. In an example, the dielectric ridge 110 includes a thickness of six pm, a height of six pm, and six um wide ridges with an etch depth of three pm.

[0067] FIGS. 1B-1E are cross sectional views of the example optical coupler 100 at cross sections B-E, respectively. Referring to FIG. IB, the optical coupler 100 includes a Si layer 120 with a channel 101 and insulator 115 at cross section B. It should be noted that Si layer 120 components other than channel 101 may not have any relevant function here. The space between the channel 101 and other silicon layer 120 components should be larger than 20um in order to avoid such components from receiving light energy. For example, the optical coupler 100 may be constructed according to Si on insulator technology. As such, the Si layer 120 may be bonded on the SiCh box layer 117 which is on the surface of a Si substrate layer 121. More than 2.0 micrometers Si02 film may cover on the top of 120 silicon layer.

[0068] Referring to FIG. 1C, the optical coupler 100 includes the waveguide inverse taper 102, the bridge taper 106, and the ridge taper 111 at cross section C. An insulator gap 116 layer separates the waveguide 102 from the bridge 106. The thickness of the insulator gap 116 affects the confinement and return loss between the waveguide 103 and the bridge 105. Ridges can be further etched into the dielectric ridge 110 as desired to tune the optical coupler 100 for coupling to the fiber. The space between the bottom of SiON ridge waveguide and the top of Si02 box layer is filled with Si02. SiN channel and silicon channel are buried in Si02 dielectric film.

[0069] Referring to FIG. ID, the waveguide inverse taper 102 has terminated prior to cross section D. Accordingly, FIG. ID depicts the bridge inverse taper 107 under the ridge taper 111. Referring to FIG. IE, the bridge inverse taper 107 has terminated prior to cross section E. As such, FIG. IE depicts the facet 112 of the dielectric ridge 110 etched into the insulator 115. The space between the bottom of SiON ridge waveguide and the top of Si02 box layer is filled with Si02 for FIG. ID and FIG. IE also. It should be noted that the structures described herein may be fabricated as part of fabrication processes that create other more complex structures.

[0070] FIG. 2A is a top view of an example optical coupler 200 including a waveguide inverse taper with an etched tip. The optical coupler 200 is similar to optical coupler 100. For example, the optical coupler 200 includes an insulator215, a waveguide 203 with a channel 201 and a waveguide inverse taper 202, a bridge 205 with a bridge taper 206, and a dielectric ridge 210 with a ridge taper 211, that are substantially similar to the insulator 115, the waveguide 103, the channel 101, the waveguide inverse taper 102, the bridge 105, the bridge taper 106, the dielectric ridge 110, and the ridge taper 111, respectively. Any components of optical coupler 200 not depicted or directly addressed are substantially similar to corresponding components in optical coupler 100.

[0071] Optical coupler 200 differs from optical coupler 100 in that the waveguide inverse taper 202 of the waveguide 203 includes a tip 204 with a partial etch. A partial etch is an etch that is applied to make the effective refractive index of the TE and TM modes equal or approximately equal. For example, the waveguide 203 is deposited into the insulator 215. It should be noted that high quality silicon crystal film cannot be grown on the silicon dioxide dielectric surface. However, two materials can be bonded together. For example, poly silicon can be deposited on the surface of SiCh by a sputtering machine. In such a case, the light propagation loss is very high, so silicon wafer bonding with SiCh on the top can be used for these purposes. A mask is then used to etch away a portion of the tip 204 of the waveguide 203. More insulator 215 can then be deposited before etching/depositing the bridge 205 and the dielectric ridge 210. The etching reduces the optical confinement of the tip 204, which allows more light to enter the insulator 215 in the direction of the bridge 205. This in turn reduces both the total loss and the return loss associated with the waveguide inverse taper 202 of the waveguide 203. In an example, the etch depth of the tip 204 has a width of 0.13 pm and is etched to a depth of 0.065 pm. In an example, the partial etching taper length is 20 pm and the tip 204 width is 30 nanometers (nm).

[0072] The optical coupler 200 includes an Optical Interface 1 between the channel 201 and the bridge taper 206/ dielectric ridge 210, which is similar to Optical Interface 1 in optical coupler 100. The optical coupler 200 also includes an Optical Interface 2 at the tip 204 of the bridge inverse taper 206. However, the etch divides the Optical Interface 2 into an Optical Interface 2A at the start of the etch and Optical Interface 2B at the termination of the tip 204. Accordingly, the etch at the tip 204 extends between Optical Interface 2A and Optical Interface 2B.

[0073] The optical coupler 200 is further depicted by employing cross section B, cross section C, and cross section D. FIGS. 2B-2D are cross sectional views of the example optical coupler 200 with the etched tip at cross sections B-D, respectively. Referring first to FIG. 2B, the optical coupler 200 includes a channel 201 etched into insulator 215 at cross section B, in a manner similar to channel 101 and insulator 115, respectively, in FIG. IB. Several micrometers thick SiCh may cover the top of the channel 201. Referring to FIG. 2C, the optical coupler 200 includes the waveguide inverse taper 202, the bridge taper 206, and the ridge taper 211 at cross section C, in a manner similar to waveguide inverse taper 102, the bridge taper 106, and the ridge taper 111, respectively, in FIG. 1C. The waveguide inverse taper 202 is separated from the bridge taper 206 by an insulator gap 216 substantially similar to the insulator gap 116.

[0074] Referring to FIG. 2D, the optical coupler 200 includes the bridge taper 206 and the ridge taper 211 at cross section D, in a manner similar to the bridge taper 106 and the ridge taper 111, respectively, in FIG. 2C. As shown, the tip 204 has been etched, for example to a depth of 0.065 pm, to reduce coupling loss and/or return loss.

[0075] FIG. 3 is a top view of an example optical coupler 300 with a dielectric ridge 310 including a ridge interface 313 and a bridge 305 that extends below the ridge interface 313. The optical coupler 300 includes an insulator 315, a bridge 305 with a bridge inverse taper 307, and a dielectric ridge 310 with a ridge taper 311 and a facet 312, which may be substantially similar to the insulator 115, the bridge 105, the bridge inverse taper 107, the dielectric ridge 110, the ridge taper 111, and the facet 112, respectively of coupler 100 described above. Any components of optical coupler 300 not depicted or directly addressed are substantially similar to corresponding components in optical coupler 100 and/or 200. The dielectric ridge 310 also comprises a ridge interface 313 between the ridge taper 311 and the facet 312. As used herein, the ridge interface 313 is the point where the ridge taper 311 begins to angle toward the facet 312. In optical coupler 300, the bridge inverse taper 307 of the bridge 305 extends to the ridge interface 313. The optical coupler 300 also comprises an Optical Interface 3 at the termination/tip of the bridge inverse taper 307. Hence, the Optical Interface 3 occupies the same location as the ridge interface 313.

[0076] FIG. 4 is a top view of an example optical coupler 400 with a dielectric ridge 410 including a facet 412 and a bridge 405 that extends below the facet 412. The optical coupler 400 includes an insulator 415 , a bridge 405 with a bridge inverse taper 407, and a dielectric ridge 410 with a ridge taper 411 and a facet 412, which may be substantially similar to the substrate 115, the bridge 105, the bridge inverse taper 107, the dielectric ridge 110, the ridge taper 111, and the facet 112, respectively of coupler 100 described above. Any components of optical coupler 400 not depicted or directly addressed are substantially similar to corresponding components in optical coupler 100 and/or 200. In optical coupler 400, the bridge inverse taper 407 of the bridge 405 extends to the facet 412. The optical coupler 400 also comprises an Optical Interface 3 at the termination/tip of the bridge inverse taper 407. Hence, the Optical Interface 3 occupies the same location as the facet 412.

[0077] FIG. 5 is a graph 500 of return loss at Optical Interface 1 of example optical couplers, such as optical coupler 100, 200, 300, and/or 400 with varying insulator gap sizes between the waveguide and the bridge. Specifically, the graph 500 shows how return loss varies as the size of insulator gap 116 and/or 216 varies. The graph 500 compares return loss in decibels (dBs) versus optical signal wavelength in pm. The top five lines depict return loss for an insulator gap of 0.02 pm for a0.38 TM mode, a 0.3 TM mode, a 0.26 TM mode, a 0.22 TM mode, and a 0.18 TM mode. The middle five lines depict return loss for an insulator gap of 0.1 pm for a 0.38 TM mode, a 0.3 TM mode, a 0.26 TM mode, a 0.22 TM mode, and a 0.18 TM mode. The bottom five lines depict return loss for an insulator gap of 0.2 pm for a 0.38 TM mode, a 0.3 TM mode, a 0.26 TM mode, a 0.22 TM mode, and a 0.18 TM mode. As shown in graph 500, wider silicon waveguide widths and larger insulator gaps result in smaller reflection, and hence smaller return loss. When the bridge and ridge start before the waveguide inverse taper, the optical mode is well confined by the waveguide, the bridge and the ridge have less impact on the optical mode, and hence the reflection at Optical Interface 1 is reduced. Also, when the insulator gap is larger, the bridge and ridge impact is reduced, and hence the reflection at the interface is reduced. For return loss less than -40dB, the insulator gap should be larger than 0.1 pm with a wide waveguide width, for example 0.38 pm.

[0078] FIG. 6 is a graph 600 of the effective index for various waveguide and bridge widths of an example optical coupler, such as optical coupler 100, 200, 300, and/or 400. The graph 600 compares the effective index on the left versus the SiN bridge width in pm on the top and versus the Si waveguide width in pm on the bottom. The lines depict the effective index of the Si waveguide in TM mode and TE mode as well as the SiN bridge in TM mode and TE mode. The waveguide inverse taper and the bridge taper can be linear tapers. In this case, the taper length may be elongated to adiabatically couple the light between the fundamental mode of the silicon waveguide and that of the SiN bridge. However, the strongest coupling between the two waveguides happens when the Si waveguide and the SiN bridge have an effective index crossing. Graph 600 shows the effective index of the Si waveguide and the SiN bridge with different widths. In this example, the Si thickness is 0.22 pm and the SiN bridge width is 0.4 pm. For TE mode, the effective index crosses when the Si waveguide width is about 0.19pm and SiN bridge width about 0.7 pm. For TM mode, the effective index crosses when the Si waveguide width is about 0.16-0.17 pm and the SiN bridge width is about 0.9-1 pm. At the index crossing point, a slow taper can be used to adiabatically couple and reduce the light coupling loss. Further, the light is well confined by the Si waveguide and/or SiN bridge, and hence the taper angles the total taper length can be reduced.

[0079] FIG. 7 is a graph 700 of the coupling loss at Optical Interface 2 at various wavelengths for an example optical coupler, such as optical coupler 100, 200, 300, and/or 400. The graph 700 compares the coupling loss at Optical Interface 2 in dB versus optical signal wavelength in pm. FIG. 8 is a graph 800 of the return loss at Optical Interface 2 at various wavelengths for an example optical coupler, such as optical coupler 100, 200, 300, and/or 400. The graph 800 compares the return loss at Optical Interface 2 in dB versus optical signal wavelength in pm. Coupling loss and return loss occur at Optical Interface 2 when the waveguide inverse taper is terminated with a specific tip width. The loss and the reflection are determined by the silicon tip width and the SiN bridge width at the Optical Interface 2. This may be more severe for the TM mode because the Electromagnetic field (E-field) is in the vertical direction for the TM mode. [0080] FIG. 9 is a graph 900 of the coupling loss related to an etched tip of a waveguide inverse taper at various wavelengths for an example optical coupler, such as optical coupler 100, 200, 300, and/or 400. The graph 900 compares the coupling loss at Optical Interface 2A-2B in dB versus optical signal wavelength in pm when the tip of the Si waveguide is partially etched. FIG. 10 is a graph 1000 of the return loss related to an etched tip of a waveguide inverse taper at various wavelengths for an example optical coupler, such as optical coupler 100, 200, 300, and/or 400. The graph 1000 compares the return loss at Optical Interface 2A-2B in dB versus optical signal wavelength in pm when the tip of the Si waveguide is partially etched. A comparison of graphs 700 and 800 to graphs 900 and 1000 shows that the optical signal loss and the return loss is much smaller with partial etch to the waveguide inverse taper tip than without.

[0081] FIG. 11 is a graph 1100 of the coupling loss between the waveguide and the bridge at various wavelengths for an example optical coupler, such as optical coupler 100, 200, 300, and/or 400. The graph 1100 compares the coupling loss between the waveguide and the bridge versus optical signal wavelength in pm. The graph 1100 depicts such data for an un-etched waveguide tip in TM mode and TE mode as well as an etched waveguide tip in TM mode. [0082] FIG. 12 is a graph 1200 of the coupling loss related to the tip of the inverse taper of the bridge at various wavelengths for an example optical coupler, such as optical coupler 100, 200, 300, and/or 400. The graph 1200 compares the coupling loss at the bridge inverse taper in dB versus optical signal wavelength in pm. The graph 1200 contains lines for TE and TM modes for varying reflective indices for the dielectric ridge. FIG. 13 is a graph 1300 of the return loss related to the tip of the inverse taper of the bridge at various wavelengths for an example optical coupler, such as optical coupler 100, 200, 300, and/or 400. The graph 1300 compares the return loss at the bridge inverse taper in dB versus optical signal wavelength in pm. The graph 1300 contains lines for TE and TM modes for varying reflective indices for the dielectric ridge.

[0083] Accordingly, graphs 1200 and 1300 relate to the coupling between the inverse taper of the bridge and the dielectric ridge waveguide. The dielectric ridge can include a constant width or a taper. The dielectric ridge has a large thickness, for example 6 pm, to match modes with a single mode fiber. The dielectric ridge is partially etched, for example 3 pm, to form the ridge waveguide. The gap between the dielectric ridge and the bridge waveguide can be zero or several tenths of a micrometer. The bridge is tapered from a wide width to a narrow tip width. Narrower tip widths are better, but limited by the process capability. For example, the inverse tip width of the bridge may be 0.2 pm. The light exiting the bridge tip is confined to the dielectric ridge. However, some optical power may remain in the bridge tip. The percentage of power confined within the bridge tip is dependent on the dimension and the index of the dielectric ridge. The bridge tip waveguide can be terminated before reaching the facet. In this case, the bridge tip causes reflection and coupling loss at Optical Interface 3. The bridge tip can also be extended to the facet of the dielectric ridge. In this case, the Optical Interface 3 overlaps with the facet of the edge coupler. Graphs 1200 and 1300showthecoupling loss and return loss at Optical Interface 3. In this example, the bridge thickness is 0.4 pm, the bridge tip width is 0.2 pm, the dielectric ridge thickness is 6 pm, the partial etch depth is 3 pm, the dielectric ridge width is 6 pm, and the insulator gap between the bridge and the dielectric ridge is zero. These graphs indicate the dielectric ridge index may be set above 1.54 to ensure the coupling loss is less than 0. ldB.

[0084] FIG. 14 is a graph 1400 of the bridge and dielectric ridge confinement at various bridge widths and wavelengths for an example optical coupler, such as optical coupler 100, 200, 300, and/or 400. The graph 1400 compares the confinement in dB versus bridge width in pm. The graph 1400 contains lines for TE and TM modes for both the SiN bridge and the SiON dielectric ridge. The bridge inverse taper can be a linear taper. However, since the dielectric ridge can employ many modes, the bridge linear taper should be long to adiabatically couple between bridge fundamental mode and the dielectric ridge fundamental mode. To reduce the taper length, a non-linear taper can be used such that the light is well confined by the bridge waveguide and/or dielectric ridge. Graph 1400 shows the result of the mode confining in the bridge and/or the dielectric ridge with mode overlap. This graph 1400 supports a determination of the SiN bridge width and the SiON dielectric ridge width range that supports coupling between the components. In this width range, a long slow taper may be employed at the bridge. Otherwise, a short fast taper may be employed.

[0085] FIG. 15 is a graph 1500 of the coupling loss between the bridge and the dielectric ridge at various wavelengths for an example optical coupler, such as optical coupler 100, 200, 300, and/or 400. Graph 1500 shows the coupling loss between the bridge and the dielectric ridge in dBs versus the optical signal wavelength in pm. Once optical confinement is managed from the waveguide to the bridge and the bridge to the dielectric ridge, the dielectric ridge can be tapered to adjust the dielectric ridge width to minimize the mode mismatch loss between the dielectric ridge and the optical fiber.

[0086] FIG. 16 is a schematic diagram of an example control device 1600 for designing/manufacturing an optical coupler, such as optical coupler 100, 200, 300, and/or 400. For example, control device 1600 can be used to implement a method 1700 and/or manufacturing device 1800, for example on a SOI wafer. Hence, the control device 1600 is suitable for implementing the disclosed examples/embodiments as described herein. The control device 1600 comprises downstream ports 1620, upstream ports 1650, and/or one or more transceiver units (Tx/Rx) 1610, including transmitters and/or receivers for communicating data upstream and/or downstream over a network. The control device 1600 also includes a processor 1630 including a logic unit and/or central processing unit (CPU) to process the data and a memory 1632 for storing the data. The control device 1600 may also comprise optical-to-electrical (OE) components, electrical -to-optical (EO) components, and/or wireless communication components coupled to the upstream ports 1650 and/or downstream ports 1620 for communication of data via electrical, optical, and/or wireless communication networks.

[0087] The processor 1630 is implemented by hardware and software. The processor 1630 may be implemented as one or more CPU chips, cores (e.g., as a multi-core processor), field- programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), digital signal processors (DSPs), or any combination of the foregoing. The processor 1630 is in communication with the downstream ports 1620, Tx/Rx 1610, upstream ports 1650, and memory 1632. The Tx/Rx 1610 comprises a control module 1614. The control module 1614 implements the disclosed embodiments described herein. Specifically, the control module 1614 may be employed to control the application of masks, deposition of chemicals, and addition of etching solutions. For example, the control module 1614 can be employed to create a Si waveguide with an inverse taper, a bridge with both a taper and an inverse taper above the waveguide, and a dielectric ridge above the bridge. Accordingly, the control module 1614 may be configured to perform mechanisms to address one or more of the problems discussed above. As such, the control module 1614 improves the functionality of the control device 1600 as well as addresses problems that are specific to the optical communication arts. Further, the control module 1614 effects a transformation of the control device 1600 to a different state. Alternatively, the control module 1614 can be implemented as instructions stored in the memory 1632 and executed by the processor 1630 (e.g., as a computer program product stored on a non-transitory medium).

[0088] The memory 1632 comprises one or more memory types such as disks, tape drives, solid-state drives, read only memory (ROM), random access memory (RAM), flash memory, ternary content-addressable memory (TCAM), static random-access memory (SRAM), and other optical and/or electrical memory systems suitable for this task. The memory 1632 may be used as an over-flow data storage device, to store programs when such programs are selected for execution, and to store instructions and data that are read during program execution.

[0089] FIG. 17 is a flowchart of an example method 1700 of manufacturing an optical coupler, such as optical coupler 100, 200, 300, and/or 400, for example by employing a control device 1600 and/or a manufacturing device 1800. Method 1700 may begin when a control device determines to print one or more optical couplers onto a base, such as according to a silicon on insulator manufacturing process. The method 1700 begins by depositing substrate, such as S1O2, as desired.

[0090] At step 1701, the control device etches the insulator and deposits a silicon waveguide onto the substrate. The silicon waveguide includes a channel and terminates in a waveguide inverse taper. The silicon waveguide may comprise an inverse taper interface between the channel and the waveguide inverse taper. The control device may optionally perform a partial etch of a tip of the waveguide inverse taper. The control device may optionally deposit a layer of insulator above the silicon waveguide at step 1703 to create an insulator gap between the waveguide and a bridge. At step 1705, the control device etches the insulator and deposits the bridge above the waveguide inverse taper. The bridge comprises a bridge taper deposited over the waveguide inverse taper. The bridge taper may be deposited to extend above the inverse taper interface. The bridge may comprise SiN. The bridge comprises a bridge inverse taper deposited to extend below a dielectric ridge. At step 1707, the control device deposits a dielectric ridge above the bridge. The dielectric ridge may be deposited to extend above the inverse taper interface in the silicon waveguide. In some examples, the dielectric ridge is deposited to extend to a position between the inverse taper interface of the waveguide and a termination of the waveguide inverse taper (e.g., the tip). The dielectric ridge comprises a ridge taper, a facet, and a ridge interface between the ridge taper and the facet. In some examples, the bridge inverse taper is deposited to extend to the facet. In some examples, the bridge inverse taper is deposited to extend to the ridge interface. The dielectric ridge may comprise SiON. The silicon waveguide can then couple light to the bridge via the waveguide inverse taper. The bridge can receive the light via the bridge taper and couple light to the dielectric ridge via the bridge inverse taper. The dielectric ridge can then be used to couple the light onto an optical fiber.

[0091] FIG. 18 is an example of a manufacturing device 1800 for manufacturing an optical coupler, such as optical coupler 100, 200, 300, and/or 400. For example, the manufacturing device 1800 may perform the steps of method 1700 and/or may be implemented on and/or in conjunction with a control devicel600.The manufacturing device 1800 comprises a fabricating module 1801 for fabricating a silicon waveguide on top of a silicon on insulator (SOI) wafer, the silicon waveguide including a channel and terminating in a waveguide inverse taper. The manufacturing device 1800 also comprises a first depositing 1803 for depositing a bridge above the waveguide inverse taper. The manufacturing device 1800 also comprises a second depositing module 1805 for depositing a dielectric ridge disposed above the bridge.

[0092] A first component is directly coupled to a second component when there are no intervening components, except for a line, a trace, or another medium between the first component and the second component. The first component is indirectly coupled to the second component when there are intervening components other than a line, a trace, or another medium between the first component and the second component. The term “coupled” and its variants include both directly coupled and indirectly coupled. The use of the term “about” means a range including ±10% of the subsequent number unless otherwise stated.

[0093] It should also be understood that the steps of the exemplary methods set forth herein are not necessarily required to be performed in the order described, and the order of the steps of such methods should be understood to be merely exemplary. Likewise, additional steps may be included in such methods, and certain steps may be omitted or combined, in methods consistent with various embodiments of the present disclosure.

[0094] While several embodiments have been provided in the present disclosure, it may be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented.

[0095] In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, components, techniques, or methods without departing from the scope of the present disclosure. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and may be made without departing from the spirit and scope disclosed herein.