An optical device includes: a coupler that includes a first port, a second port, a third port, a fourth port, and a multimode interference waveguide; a first waveguide that is optically connected to the first port, the first waveguide being configured to guide light that is input to the coupler via the first port; a second waveguide that is optically connected to the second port, the second waveguide being configured to guide light that is input to the coupler via the second port; a third waveguide that is optically connected to the third port, the third waveguide being configured to guide light that is output from the coupler via the third port; and a fourth waveguide that is optically connected to the fourth port and, the fourth waveguide being configured to guide light output from the coupler via the fourth port.

A photonic integrated circuit comprises an optical deinterleaver, including an input region, a dispersive region, and at least two output regions. The input region is adapted to receive an input optical signal including a plurality of channels. The dispersive region is optically coupled to the input region to receive the input optical signal. The dispersive region includes an inhomogeneous arrangement of a first material and a second material to structure the dispersive region to separate the input optical signal into a plurality of multi-channel optical signals, including a first multi-channel optical signal and a second multi-channel optical signal. The at least two output regions, include a first out region and a second output region optically coupled to the dispersive region. The first output region is positioned to receive the first multi-channel optical signal and the second output region is positioned to receive the second multi-channel optical signal.

An optical structure comprising a multimode interference waveguide section, the multimode interference waveguide section comprising an input face, an output face and sidewalls extending therebetween, the sidewalls extending substantially parallel to a length axis; at least one input optical waveguide abutting the input face and spaced apart from the sidewalls; at least one output optical waveguide abutting the output face and spaced apart from the sidewalls; the input face being divided into first and second input face shoulder portions arranged on opposite sides of the at least one input optical waveguide; and the output face being divided into first and second output face shoulder portions arranged on opposite sides of the at least one output optical waveguide; the optical structure further comprising at least one external reflector appendage, the at least one external reflector appendage comprising a reflector portion integrally extending from a shoulder portion and an appendage waveguide integrally extending from the reflector portion along an axis inclined to the length axis, the reflector portion comprising a reflector wall arranged such that light travelling parallel to the length axis which is incident on the reflector wall is reflected into the appendage waveguide.

A method includes etching a silicon layer to form a silicon slab and an upper silicon region over the silicon slab, and implanting the silicon slab and the upper silicon region to form a p-type region, an n-type region, and an intrinsic region between the p-type region and the n-type region. The method further includes etching the p-type region, the n-type region, and the intrinsic region to form a trench. The remaining portions of the upper silicon region form a Multi-Mode Interferometer (MMI) region. An epitaxy process is performed to grow a germanium region in the trench. Electrical connections are made to connect to the p-type region and the n-type region.

Embodiments of techniques for inverse design of physical devices are described herein, in the context of generating designs for photonic integrated circuits (including a multi-channel photonic demultiplexer). In some embodiments, an initial design of the physical device is received, and a plurality of sets of operating conditions for fabrication of the physical device are determined. In some embodiments, the performance of the physical device as fabricated under the sets of operating conditions is simulated, and a total performance loss value is backpropagated to determine a gradient to be used to update the initial design. In some embodiments, instead of simulating fabrication of the physical device under the sets of operating conditions, a robustness loss is determined and combined with the performance loss to determine the gradient.

A large-scale single-photonics-based optical switching system that occupies an area larger than the maximum area of a standard step-and-repeat lithography reticle is disclosed. The system includes a plurality of identical switch blocks, each of is formed in a different reticle field that no larger than the maximum reticle size. Bus waveguides of laterally adjacent switch blocks are stitched together at lateral interfaces that include a second arrangement of waveguide ports that is common to all lateral interfaces. Bus waveguides of vertically adjacent switch blocks are stitched together at vertical interfaces that include a first arrangement of waveguide ports that is common to all vertical interfaces. In some embodiments, the lateral and vertical interfaces include waveguide ports having waveguide coupling regions that are configured to mitigate optical loss due to stitching error.

An optical circuit for routing a signal includes a coupler and first and second waveguides. The coupler has an input for the signal and has first and second outputs. The first waveguide has a first optical connection to the first output, and the second waveguide has a second optical connection to the second output. Both waveguides have the same propagation length. The first and second waveguides include different widths at the respective optical connections to the respective outputs. This coupler can be used with another input couplers, two additional waveguides, and two 2×2 output couplers to provide a 90-degree hybrid for mixing signal light and local oscillator light in a coherent receiver or the like.

A method includes etching a silicon layer to form a silicon slab and an upper silicon region over the silicon slab, and implanting the silicon slab and the upper silicon region to form a p-type region, an n-type region, and an intrinsic region between the p-type region and the n-type region. The method further includes etching the p-type region, the n-type region, and the intrinsic region to form a trench. The remaining portions of the upper silicon region form a Multi-Mode Interferometer (MMI) region. An epitaxy process is performed to grow a germanium region in the trench. Electrical connections are made to connect to the p-type region and the n-type region.

An optical apparatus comprising an integrated germanium photodetector associated with a silicon nitride launch waveguide, the integrated germanium photodetector comprising a silicon layer, a germanium layer disposed atop the silicon layer, a plurality of conductive vias, at least one conductive via of the plurality of conductive vias being disposed atop the germanium layer, and a plurality of metal contacts each interconnected to each of the plurality of conductive vias; wherein the silicon nitride launch waveguide extends over a length of the silicon layer, and such that to create a coupling region between the silicon nitride launch waveguide and the germanium layer; and wherein, when an optical signal is launched into the silicon nitride launch waveguide, the optical signal is caused to be coupled into the integrated germanium photodetector at the coupling region, such that to be absorbed by the germanium layer.

A semiconductor optical modulator includes a modulation region and a non-modulation region. A first width of a first ground electrode in the non-modulation region is larger than a second width of the first ground electrode in the modulation region. A third width of a second ground electrode in the non-modulation region is larger than a fourth width of the second ground electrode in the modulation region. In the non-modulation region, a first insulating layer is disposed between a first optical waveguide and a first traveling wave electrode and between a second optical waveguide and a second traveling wave electrode. For this reason, a bandwidth of the semiconductor optical modulator can be widened.