OUTPUT GRATING COUPLERS ON PLANAR WAVE-GUIDES AS INTEGRATED OPTICAL CHEMICAL SENSORS

We have demonstrated that output grating couplers on thin SiO2-TiO2 waveguides are sensors which respond (i) with sub-monomolecular sensitivity to the adsorption of molecules out of a gaseous or liquid sample covering the waveguide in the grating region, and (ii) to changes in the refractive index of the sample. The effects (i) and (ii) induce changes in the effective refractive indices of the guided TE0 and TM0 modes, to which the sensors respond with a change in direction of the outcoupled beams, which were measured with position-sensitive detectors having (sub)-milli-second response times. Waveguides coated with thin chemoresponsive adlayers are proposed as sensitive (bio)chemical sensors. Work on immunosensors or immunoassays is in progress. © 1990.