A photonic integrated circuit is provided that may include a substrate; one or more optical sources, on the substrate, to output light associated with a corresponding one or more optical signals; one or more waveguides connected to the one or more optical sources; a multiplexer connected to the one or more waveguides; and one or more light absorptive structures, located on the substrate adjacent to one of the one or more optical sources, one of the one or more waveguides, and/or the multiplexer, to absorb a portion of the light associated with at least one of the corresponding one or more optical signals.

An optical waveguide crosspoint comprising first and second single multimode interference sections, each single multimode interference section comprising an input face, an output face and sidewalls extending therebetween, the distance between the input face and output face for each single multimode interference section being the; length of the multimode interference section, the lengths of the first and second multimode interference sections being L1 and L2 respectively; at least one primary input optical waveguide connected to the input face of the first single multimode interference section; at least one primary output optical waveguide connected to the output face of the first single multimode interference section; the first single multimode interference section comprising a symmetry axis extending from the center of the input face to the center of the output face; at least one secondary input optical waveguide connected to the input face of the second single multimode interference section; at least one secondary output optical waveguide connected to the output face of the second single multimode interference section; the second single multimode interference section comprising a symmetry axis extending from the center of the input face to the center of the output face; the first and second single multimode interference sections intersecting to form an L shaped compound multimode interference structure; the width of each single multimode interference section in a direction normal to Its symmetry axis being less than 15% of the length of the other single multimode interference section.

A compressive/transform imager comprising a lens array positioned above input ports for collecting light into the input ports, waveguides routing the light from the input port to waveguide mixing regions (e.g. multi-mode interference couplers), and detectors for receiving outputs of the waveguide mixing regions.

Systems and methods described herein are directed to polarization separation of laser signals and/or incoming light signals associated with an imaging system, such as a Light Detection and Ranging (LIDAR) system. Example embodiments describe a system configured to direct incoming light signals to a polarization separator and capturing the two polarization states of the incoming light signals. In some instances, the laser signal may be converted into two different polarization states. The system may individually process the two polarization states of the incoming light signals along with the corresponding polarization state of the laser reference signal to extract information associated with reflecting objects within the field-of-view of the imaging system. The polarization separator may be a birefringent crystal positioned adjacent to an edge of a photonic integrated circuit (PIC) that is used for processing outgoing and incoming light signals associated with the imaging system.

A polarizing device includes: a first waveguide to guide input light, a second waveguide to guide TE-polarized light,
wherein the second waveguide includes a tapered input portion to polarization-selectively couple TE-polarized light from the first waveguide to the second waveguide, wherein the tapered input portion symmetrically overlaps the first waveguide, and the thickness of the tapered input portion has been selected to substantially prevent coupling of TM-polarized light from the first waveguide to the second waveguide, wherein the refractive index of the second waveguide is higher than the refractive index of the first waveguide.

A device includes a scattering structure and a collection structure. The scattering structure is arranged to concurrently scatter incident electromagnetic radiation along a first scattering axis and along a second scattering axis. The first scattering axis and the second scattering axis are non-orthogonal. The collection structure includes a first input port aligned with the first scattering axis and a second input port aligned with the second scattering axis. A method includes scattering electromagnetic radiation along a first scattering axis to create first scattered electromagnetic radiation and along a second scattering axis to create second scattered electromagnetic radiation. The first scattering axis and the second scattering axis are non-orthogonal. The first scattered electromagnetic radiation is detected to yield first detected radiation and the second scattered electromagnetic radiation is detected to yield second detected radiation. The first detected radiation is phase aligned with the second detected radiation.

A coherent beam coupled laser diode array includes an array of laser diodes. Each diode emits a beam propagating along a beam path. An array of collimation optics is included. Each of the collimation optics collimates one beam. A first lenslet array is included. Each lenslet refracts a portion of one beam and a portion of a different beam from the array. A partially reflecting mirror is included. A first portion of each beam propagates through the partially reflecting mirror and a second portion of each beam is reflected back toward the first lenslet array. The second portion of each beam reflected propagates back through the first lenslet array and the collimation optics and into one of the diodes in the array of laser diodes, thereby creating an optical cross coupling. A second lenslet array collimates each beam propagating through each lenslet to form a single laser beam.

A balanced homodyne detection optical circuit according to the present disclosure is a planar optical waveguide circuit in which a circuit made of an optical waveguide including a dielectric or a semiconductor is formed on a substrate, the balanced homodyne detection optical circuit including an input port of local oscillator light and an input port of measurement light (squeezed light (including excitation light)), wherein a wavelength demultiplexing circuit which demultiplexes only the measurement light is arranged immediately after the input port of measurement light, a 50% multiplexing/demultiplexing circuit is arranged which causes squeezed light having been demultiplexed by the wavelength demultiplexing circuit and the local oscillator light to respectively branch at a branching ratio of 50% and to interfere with each other, and two output ports are arranged to which two outputs from the 50% multiplexing/demultiplexing circuit are guided.

An optical modulator that uses adiabatic tapers to change the width of the waveguides between multimode waveguides and single mode waveguides on a low-loss, e.g. thin-film lithium niobate, electro-optic platform. The architecture enables the utilization of the fundamental mode of multimode wide optical waveguides that have lower optical propagation loss without sacrificing the benefit of the signal integrity and ease of control of single mode operation.

In one example, an optoelectronic assembly may include a laser array, an amplifier array, and a multimode interference coupler optically coupling the laser array and the amplifier array. The laser array may include at least one primary laser and at least one spare laser configured to be activated if the primary laser fails. The amplifier array may include at least two amplifiers configured to amplify optical signals received from the laser array.