Abstract: An optical coupling apparatus for coupling an optical fiber to a photonic chip is described. The apparatus includes a collimating microlens for collimating light from the optical fiber; a polarization splitting beam displacer for separating the light collimated by the collimating microlens into orthogonally polarized X and Y component beams; at least one focusing microlens for directing the X and Y component beams separately onto the photonic chip; and first and second surface grating couplers (SGCs) orthogonally disposed on the photonic chip and configured for operation in a same polarization state, for coupling the X and Y component beams, respectively, to the photonic chip.

Abstract: An optical apparatus for compensating a measurement inaccuracy of polarization dependent loss (PDL) is described. The apparatus comprises a first polarization rotator splitter (PRS) for splitting an input beam into orthogonally polarized X and Y component beams and rotating one of the X and Y component beams to be in the same polarization as the other component beam; first and second circuits for processing the X and Y component beams respectively; a first polarization rotator combiner (PRC) for combining the X and Y component beams processed respectively by the first and second circuits into an output beam, one of the X and Y component beams being rotated to be orthogonally polarized with respect to the other component beam.

Abstract: An optical waveguide termination includes a light-receiving inlet for receiving light to be terminated, a rib waveguide extending from the inlet, a doped, light-absorbing slab supporting the rib waveguide for absorbing light from the rib waveguide, and a tip at an end of the rib waveguide. The optical waveguide termination exhibits low back-reflection.

Abstract: An optical waveguide termination comprising a light-receiving inlet for receiving light to be terminated, a curved section extending from the inlet and having a continuously decreasing radius of curvature, and a light-terminating tip at an end of the curved section. The curved section may define a spiral waveguide, for example a logarithmic spiral, having a waveguide width that continuously decreases from the inlet to the tip.

Abstract: A photonic platform based polarization controller providing a fixed target polarization is disclosed. The polarization controller has a polarization rotator splitter splitting the beam into first and second feeds corresponding to first and second orthogonal polarization components. A first Mach-Zehnder interferometer (MZI) stage provides a first phase delay between the first and second feeds based on a first control signal, and a first mixer mixes the first and second feeds to provide third and fourth feeds. A second MZI stage provides a second phase delay between the third and fourth feeds based on a second control signal, and a second mixer mixes the third and fourth feeds to provide fifth and sixth feeds. A third MZI stage provides a third phase delay between the fifth and sixth feeds based on a third control signal, and a third mixer mixes the fifth and sixth feeds to provide the fixed target polarization. An optical tap splits a portion of the beam.

Abstract: A photonic platform includes a substrate, a buried oxide layer on the substrate, a first optical layer on the buried oxide layer, the first optical layer including one or more waveguides shaped as rib waveguides protruding upwardly from a common underlying slab and a second optical layer spaced above the first optical layer, the second optical layer defining an upper waveguide that crosses over the one or more partially etched waveguides. A low-loss photonic switch may be made using a silicon photonic platform implementing this waveguide crossing.

Abstract: A photonic integrated circuit (PIC) comprises an optical switch, a plurality of input edge couplers comprising a first input edge coupler and coupled to the optical switch, a plurality of input surface grating couplers (SGCs) comprising a first input SGC and coupled to the optical switch, a plurality of output edge couplers comprising a first output edge coupler and coupled to the optical switch, and a plurality of output SGCs comprising a first output SGC and coupled to the optical switch. A method of fabricating a PIC comprises patterning and etching a silicon substrate to produce a first optical switch, a first surface grating coupler (SGC) coupled to the first optical switch, and a first edge coupler coupled to the first optical switch.

Abstract: Aspects of the present disclosure involve coherently mixing information in a first optical signal with information from one or more other optical signals, the optical signals being synchronous, to generate a mixed optical signal that obfuscates the information of the first optical signal. Each of the other optical signals is likewise mixed with a combination of the first and/or other optical signals resulting in a collection of mixed optical signals, none of which resemble the original first and other optical signals. When each of the mixed optical signals is transmitted in a separate optical fiber, then eavesdropping on only a single fiber cannot yield an unambiguous recovery of any one of the original optical signals.

Abstract: A waveguide crossing includes a first waveguide and a second waveguide intersecting the first waveguide such that a gap equal to a width of the second waveguide is formed in the first waveguide, the second waveguide having a centerline defining a plane of symmetry. The first waveguide has a first waveguide section through which a single optical mode propagates, followed by a first non-adiabatic diverging taper, followed by a second waveguide section wider than the first waveguide section through which two even-order optical modes propagate, followed by a second non-adiabatic diverging taper, followed by a third waveguide section wider than the second waveguide section through which three even-order optical modes propagate. The three even-order modes synthesize to form a quasi-Gaussian beam that self-replicates symmetrically across the gap, thereby providing a low-loss waveguide crossing useful for photonic switching.

Abstract: Embodiments are provided for an improved 2×1 switch cell design with integrated photodiode for off-state monitoring. In an embodiment, am optical switch comprises a 2×1 multi-mode interferometer (MMI) coupler including two input waveguides jointly coupled to an output waveguide, and a photodetector coupled to an edge of a first waveguide of the input waveguides, and positioned next to a side of the output waveguide. In another embodiment, an optical chip comprises two input waveguides parallel to each other, and an output waveguide coupled to the two input waveguides. The optical chip further includes a photodetector coupled to a first waveguide of the two input waveguides, and positioned next to the output waveguide, and a branch waveguide extending from the first waveguide into the photodetector.

Abstract: An optical device comprises a first optical coupler configured to receive a light signal and provide a first output and a second output, a first optical waveguide in optical communication with the first output and configured to provide a first optical path for a first portion of the light signal, and a second optical waveguide in optical communication with the second output and configured to provide a second optical path for a second portion of the light signal, wherein the first optical waveguide is configured to provide a phase differential between the first optical path and the second optical path, wherein the second optical waveguide is positioned according to a lateral thermal diffusion length associated with the first optical waveguide, and wherein the lateral thermal diffusion length is a spreading distance of a thermal effect in a direction about perpendicular to the first optical path.

Abstract: An optical attenuator and/or optical terminator is provided. The device includes an optical channel having two regions with different optical properties, such as an undoped silicon region which is less optically absorptive and a doped silicon region which is more optically absorptive. Other materials may also be used. A facet at the interface between the two regions is oriented at a non-perpendicular angle relative to a longitudinal axis of the channel. The angle can be configured to mitigate back reflection. Multiple facets may be included between different pairs of regions. The device may further include curved and/or tapers to further facilitate attenuation and/or optical termination.

Abstract: A photonic integrated circuit (PIC) comprises an optical switch, a plurality of input edge couplers comprising a first input edge coupler and coupled to the optical switch, a plurality of input surface grating couplers (SGCs) comprising a first input SGC and coupled to the optical switch, a plurality of output edge couplers comprising a first output edge coupler and coupled to the optical switch, and a plurality of output SGCs comprising a first output SGC and coupled to the optical switch. A method of fabricating a PIC comprises patterning and etching a silicon substrate to produce a first optical switch, a first surface grating coupler (SGC) coupled to the first optical switch, and a first edge coupler coupled to the first optical switch.

Abstract: An optical coupling apparatus for coupling an optical fiber to a photonic chip is described. The apparatus includes a collimating microlens for collimating light from the optical fiber; a polarization splitting beam displacer for separating the light collimated by the collimating microlens into orthogonally polarized X and Y component beams; at least one focusing microlens for directing the X and Y component beams separately onto the photonic chip; and first and second surface grating couplers (SGCs) orthogonally disposed on the photonic chip and configured for operation in a same polarization state, for coupling the X and Y component beams, respectively, to the photonic chip.

Abstract: A method for photonic device includes an optical macromodule substrate including optical interconnects and a first photonic integrated circuit (PIC) including a first photonic switch, where the first PIC is mechanically coupled to the optical macromodule substrate and optically coupled to the optical interconnect. The photonic device also includes a PIC controller electrically coupled to the first PIC.

Abstract: A tunable optical filter including a first coupler configured divide an optical signal into a first portion and a second portion, a first waveguide configured to receive the first portion of the optical signal, a second waveguide configured to receive the second portion of the optical signal, an adjustable phase element operatively coupled to the first waveguide for adjusting an optical path length of the first waveguide, a P-I-N junction operatively coupled to one of the first waveguide and the second waveguide for introducing a loss into one of the first portion of the optical signal and the second portion of the optical signal, and a second coupler operatively coupled to the first waveguide and the second waveguide, wherein the second coupler is configured to recombine the first portion of the optical signal with the second portion of the optical signal to generate a spectrally modulated optical signal.

Abstract: Crosstalk can be suppressed in photonic switching fabrics by activating unused photonic elements in a manner that manipulates the inactive connections and inhibits the propagation of cross-talk over the switching fabric. For example, unused photonic elements can be set to a cross or bar configuration to block first and second order crosstalk from propagating to the output ports, thereby reducing noise in the output signals. All of the unused elements can be activated in order to maximize crosstalk suppression. Alternatively, fewer than all of the unused elements may be activated to achieve a balance between crosstalk suppression and power conservation. Photonic switch architectures can be configured to use pre-determined cross-talk suppression maps (e.g., patterns of activated unused cells) for the various switching configurations, which may be computed using a recursive algorithm.

Abstract: Recursive optimization algorithms can be used to determine which idle photonic switching elements to configure in N×N switching fabrics to achieve crosstalk suppression. Different algorithms are used to achieve different levels of optimization. Embodiment full optimization techniques may configure all inactive cells to reduce crosstalk, and consequently may provide the best noise performance and highest power usage. Partial optimizations may configure fewer than all inactive cells to reduce crosstalk, and may provide sub-optimal noise performance at lower power usages. Differential partial optimization algorithms configure inactive cells in different stages of a photonic switching fabric. Fewer than all cells in a given stage may be configured by some algorithms.

Abstract: An optical device comprises a first optical coupler configured to receive a light signal and provide a first output and a second output, a first optical waveguide in optical communication with the first output and configured to provide a first optical path for a first portion of the light signal, and a second optical waveguide in optical communication with the second output and configured to provide a second optical path for a second portion of the light signal, wherein the first optical waveguide is configured to provide a phase differential between the first optical path and the second optical path, wherein the second optical waveguide is positioned according to a lateral thermal diffusion length associated with the first optical waveguide, and wherein the lateral thermal diffusion length is a spreading distance of a thermal effect in a direction about perpendicular to the first optical path.

Abstract: An embodiment waveguide polarization rotator includes an optical waveguide and an overlay strip. The optical waveguide has an input end and an output end oppositely disposed thereon. The optical waveguide is operable to receive, at the input end, an input optical signal having a mode having an input polarization. The optical waveguide is further operable to generate, at the output end, an output optical signal having an output polarization orthogonal to the input polarization. The overlay strip is disposed over and non-orthogonally crosses the optical waveguide. The overlay strip has a first end laterally offset from the optical waveguide by a first offset distance and a second end laterally offset from the optical waveguide by a second offset distance.