A sensor system having coupling structures is disclosed. The system includes an input coupling structure, an interaction region, and an output coupling structure. The input coupling structure is configured to receive emitted light at a selected coupling efficiency and may provide filtering of the emitted light for a selected wavelength. The interaction region is coupled to the input coupling structure and configured to interact the light from the input coupling structure with a specimen. The output coupling structure is coupled to the interaction region and configured to provide interacted light from the interaction region to the detector.