Aspects of the present disclosure are directed toward designs and methods improving optical sensing, wavelength division multiplexed (WDM) telecommunication transceivers, WDM add/drops, and spectrometer techniques that may benefit from a stable wavelength reference. The disclosed designs and methods are useful in the manufacture of a stable wavelength reference that may compensate for temperature variations.

A system may include a polarization rotator combiner. The polarization rotator combiner may include a first stage, a second stage, and a third stage. The first stage may receive a first component of light with a TE00 polarization and a second component of light with the TE00 polarization. The first stage may draw optical paths of the first and second components together. The second stage may receive the first component and the second component from the first stage. The second stage may convert the polarization of the second component from the TE00 polarization to a TE01 polarization. The third stage may receive the first component and the second component from the second stage. The third stage may convert polarization of the second component from the TE01 polarization to a TM00 polarization. The third stage may output the first component and output the second component.

Photonic devices, photonic integrated circuits, optical elements, and techniques of making and using the same are described. A photonic device includes an input region adapted to receive an optical signal including a multiplexed channel characterized by a distinct wavelength, a dispersive region optically coupled with the input region to receive the optical signal, the dispersive region including a plurality of sub-regions defined by an inhomogeneous arrangement of a first material and a second material, and a plurality of output regions optically coupled with the input region via the dispersive region. The plurality of sub-regions can include an input channel section, one or more coupler sections, and one or more branching sections. The plurality of sub-regions together can configure the photonic device to demultiplex the optical signal and to isolate the multiplexed channel at a first output region of the plurality of output regions.

Various polarization rotator splitter (PRS) configurations are disclosed. In an example embodiment, a system includes a PRS that includes a silicon nitride (SiN) rib waveguide core that includes a rib and a ridge that extends vertically above the rib, the SiN rib waveguide core having a total height h.sub.SiN from a bottom of the rib to a top of the ridge, a rib height h.sub.rib from the bottom of the rib to a top of the rib, a rib width w.sub.rib, and a top width w.sub.SiN of the ridge. The rib width w.sub.rib varies along at least a portion of a length of the SiN rib waveguide core.

A wavelength locker includes first and second waveguides to guide light. The wavelength locker also includes a multimode interference (MMI) coupler having a number of inputs and outputs. First and second inputs of the MMI coupler are coupled to outputs of the first and second waveguides. The MMI coupler merges light from the first and second waveguides to generate an interference pattern of light. The MMI coupler then outputs a plurality of phase shifted versions of the interference pattern. The wavelength locker also includes an interference pattern selector configured to receive signals corresponding, respectively, to light output from the outputs of the MMI coupler. The interference pattern selector is also configured to select one or more outputs of the MMI coupler based on power levels of the interference patterns output from the MMI coupler and a predetermined frequency of a telecommunications frequency grid.

In an optical modulator including an FPC for performing electrical connection with an external circuit substrate, to maintain high light transmission quality by appropriately driving the optical modulator even when the reflection of a radio frequency signal occurs in a connection portion between the FPC and the main body of the optical modulator. Provided is an optical modulator including a flexible printed circuit for performing electrical connection with a circuit substrate, in which the flexible printed circuit includes at least one wire pattern for propagating a radio frequency signal, and the wire pattern includes at least one radio frequency attenuation portion for attenuating power of the radio frequency signal by a predetermined amount.

Methods and systems for a polarization immune wavelength division multiplexing demultiplexer are disclosed and may include, in an optoelectronic transceiver having an input coupler, a demultiplexer, and an amplitude scrambler: receiving input optical signals via the input coupler, communicating the input optical signals to the amplitude scrambler via waveguides, configuring the average optical power in each of the waveguides utilizing the amplitude scrambler, and demultiplexing the optical signals utilizing the demultiplexer. The amplitude scrambler may include phase modulators and a coupling section. The phase modulators may include sections of P-N junctions in the two waveguides. The demultiplexer may include a Mach-Zehnder Interferometer. The demultiplexed signals may be received utilizing photodetectors. The input coupler may include a polarization splitting grating coupler. The average optical power may be configured above which demultiplexer control circuitry is able to control the demultiplexer to process incoming optical signals.

Photonic devices, photonic integrated circuits, optical elements, and techniques of making and using the same are described. A photonic device includes an input region adapted to receive an optical signal including a multiplexed channel characterized by a distinct wavelength, a dispersive region optically coupled with the input region to receive the optical signal, the dispersive region including a plurality of sub-regions defined by an inhomogeneous arrangement of a first material and a second material, and a plurality of output regions optically coupled with the input region via the dispersive region. The plurality of sub-regions can include an input channel section, one or more coupler sections, and one or more branching sections. The plurality of sub-regions together can configure the photonic device to demultiplex the optical signal and to isolate the multiplexed channel at a first output region of the plurality of output regions.

A thermally tunable waveguide including an optical waveguide and a heater is provided. The optical waveguide includes a phase shifter. The heater is disposed over the optical waveguide. The heater includes a heating portion, pad portions and tapered portions. The heating portion overlaps with the phase shifter of the optical waveguide. The pad portions are disposed aside of the heating portion. Each of the pad portions is connected to the heating portion through one of the tapered portions respectively.

Embodiments herein relate to photonic integrated circuits with an on-chip optical isolator. A photonic transmitter chip may include a laser and an on-chip isolator optically coupled with the laser that includes an optical waveguide having a section coupled with a magneto-optic liquid phase epitaxy grown garnet film. In some embodiments, a cladding may be coupled with the garnet film, the on-chip isolator may be arranged in a Mach-Zehnder interferometer configuration, the waveguide may include one or more polarization rotators, and/or the garnet film may be formed of a material from a rare-earth garnet family. Other embodiments may be described and/or claimed.