A photonic coupler includes an input coupling section, an output coupling section, and a multimode interference (MMI) waveguide section. The input coupling section is adapted to receive an input optical signal along an input waveguide channel. The output coupling section is adapted to output a pair of output optical signals along output waveguide channels. The output optical signals having output optical powers split from the input optical signal. The MMI waveguide section is optically coupled between the input and output coupling sections. Notched waveguide sections may each be disposed between the MMI waveguide section and a corresponding one of the input or output coupling sections and/or the MMI waveguide section may include curvilinear sidewalls.

An optical device includes a modulator and a tap coupler. The modulator includes an optical waveguide that is formed of a thin-film lithium niobate (LN) substrate and through which light passes, and an electrode that applies voltage to the optical waveguide, and modulates a phase of light that passes through the optical waveguide in accordance with an electric field in the optical waveguide, where the electric field corresponds to the voltage. The tap coupler includes at least a part formed of the thin-film LN substrate, and splits a part of the light that passes through an inside of the optical waveguide. The tap coupler includes a delayed interferometer that splits a part of the light that passes through the optical waveguide, at a split ratio corresponding to a phase difference of light that passes through an inside of the tap coupler from the optical waveguide.

Embodiments of the present disclosure are directed toward techniques and configurations for optical couplers comprising a first optical waveguide and a second optical waveguide coupled to form a 2×2 optical unitary matrix to receive a respective first input optical signal and a second input optical signal. In embodiments the first optical waveguide and second optical waveguide form arms that converge alongside each other to direct the first input optical signal and the second input optical signal along a path that integrates a plurality of tunable phase shifters to transform the first input optical signal or the second input optical signal into a first output optical signal and second output optical signal to be output from the 2×2 optical unitary matrix. Additional embodiments may be described and claimed.

Configurations for an interferometric device used for multiplexing and de-multiplexing light are disclosed. The interferometric device may include a first input waveguide, a second input waveguide, an interferometric waveguide, and an output waveguide. A fundamental mode of light may be launched into the first and second input waveguides, and the interferometric waveguide may receive the fundamental mode and generate a higher order mode of light, where the two modes of light may be superimposed while propagating through the interferometric waveguide. The two modes of light may be received at an output waveguide that collapses the two modes into a single mode. The light propagating through the interferometric device may be used for increasing optical power even though the wavelengths of light may be different from one another. Additionally, the interferometric device may reduce coherent noise.

A method for making a multimode interference (MMI) coupler with an arbitrary desired splitting ratio includes forming a thin-film of silicon-nitride material overlying a SOI substrate. The method further includes obtaining geometric parameters of a standard MIMI coupler including a rectangular MMI block and one input port and two output ports in taper shape with one of standard splitting ratios under self-imaging principle which is close to the desired splitting ratio. Additionally, the method includes tunning the input port to an off-center position at front edge of the MMI block. The method further includes making a first output port to a first off-center position flushing with a side edge of the MMI block, adjusting a second output port to a second off-center position. The method includes tunning the MMI block to obtain optimized geometric parameters for approaching the selected arbitrary splitting ratio, and etching the thin-film of silicon-nitride material.

A method for making a multimode interference (MMI) coupler with an arbitrary desired splitting ratio includes forming a thin-film of silicon-nitride material overlying a SOI substrate. The method further includes obtaining geometric parameters of a standard MIMI coupler including a rectangular MMI block and one input port and two output ports in taper shape with one of standard splitting ratios under self-imaging principle which is close to the desired splitting ratio. Additionally, the method includes tunning the input port to an off-center position at front edge of the MMI block. The method further includes making a first output port to a first off-center position flushing with a side edge of the MMI block, adjusting a second output port to a second off-center position. The method includes tunning the MMI block to obtain optimized geometric parameters for approaching the selected arbitrary splitting ratio, and etching the thin-film of silicon-nitride material.

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.

An optoelectronic chip includes optical inputs having different passbands, a photonic circuit to be tested, and an optical coupling device configured to couple said inputs to the photonic circuit to be tested.

An optical 90-degree hybrid includes two splitters, two combiners and four arm waveguides that connect output ports of the splitters and input ports of the combiners. Each of the splitters, the arm waveguides, and the combiners is a part of an optical waveguide. The optical waveguide is configured so that the phase error generated in the splitters due to wavelength change is suppressed by the phase error generated in the arm waveguides due to the wavelength change. The optical waveguide is further configured so that the phase error generated in the splitters due to deviation of a structure parameter from a certain value (e.g., design value) is suppressed by the phase error generated in the arm waveguides due to the deviation.

There is provided a device (300;500;700) for collecting fluorescent light (322) emitted by particles (304) in a medium (302). The device (300;500;700) comprises a substrate (308) having a chamber (306) for holding the medium (302) including the particles (304) being capable of emitting fluorescent light (322). A first waveguide (310), which is arranged to receive and guide excitation light along a first direction (313), extends through the chamber (306). Fluorescent light (322) emitted by the particles (304) following an excitation is collected by the first waveguide (310). The device (300;500;700) further comprises a coupler (316;516) which includes a second waveguide (317) arranged to output collected fluorescent light (326) at one of its ends (318). The second waveguide (317) is arranged in relation to the first waveguide (310) such that collected fluorescent light (324) travelling in a direction opposite to the first direction (312) is coupled out from the first waveguide (310) directly into the second waveguide (317).