Athermal wavelength stability monitor using a detraction grating

An optical device, comprising:

• a planar waveguide comprising:
• a first material, and
• a second athermal material different than the first material and adjacent to the first material, the planar waveguide defining:
• an input light path;
• and
• an output light path;
• an input waveguide configured to direct light into the planar waveguide, the light propagating on the input light path;
• a diffraction grating configured to reflect light received from the planar waveguide to propagate on the output light path;
• a first output waveguide configured to receive the reflected light from the planar waveguide and reflected from the diffraction grating;
• and
• a second output waveguide configured to receive the reflected light from the diffraction grating;
• wherein
• the input waveguide, the first output waveguide, and the second output waveguide are located on a Rowland circle.

A method for monitoring wavelengths in an optical sensing system, the method comprising:

• transmitting one or more control signals to one or more light sources;
• emitting light from the one or more light sources through one or more input waveguides and along one or more input light paths, wherein the emitted light is based on the one or more control signals;
• directing a first portion of light to a sample;
• directing a second portion of light to a planar waveguide, wherein the second portion of light propagates through the planar waveguide along one or more output light paths, the planar waveguide comprising:
• a first material, and
• a second athermal material that is adjacent to the first material and different than the first material;
• reflecting the second portion of light from a diffraction grating and through the planar waveguide;
• receiving the light from the planar waveguide, via one or more output waveguides, at one or more detectors;
• generating, by the one or more detectors, one or more detector signals indicative of the light received by the one or more detectors;
• determining a monitored wavelength from the one or more detector signals;
• determining a difference between the monitored wavelength and a target wavelength;
• and
• generating one or more adjusted control signals based on the difference between the monitored wavelength and the target wavelength;
• wherein:
• the emitted light is based on the one or more control signals;
• and
• the second portion of light propagates through the planar waveguide along one or more output light paths.