Integrated bound-mode spectral sensors with chirped gratings

A spectral sensor array, comprising:

• a planar waveguide on a substrate;
• a continuously variable chirped input coupling grating, wherein the continuously variable chirped input coupling grating comprises a chirp that has a continuous variation in periodicity in both transverse and longitudinal directions to provide a spectrally selective coupling of incident light that originates from an external source with respect to the spectral sensor array into the planar waveguide;
• a restrictor to restrict angular acceptance of the incident light to the chirped input coupling grating;
• an output coupling grating;
• and
• an array of photodetectors arranged to receive the light coupled out of the waveguide to measure/measure a spectrum of a source of the incident light.