Integrated optical ring resonator with micromechanical diaphragms for pressure sensing

An optical pressure sensor has been fabricated which uses an integrated-optical ring resonator to measure the strain induced in a micromachined silicon diaphragm. A silicon substrate is etched from the side opposite the silicon oxynitride optical waveguides to produce a rectangular diaphragm whose long edge lies underneath a straight section in the ring. Pressure-induced changes in the resonant frequency of the ring are measured using a frequency swept laser diode. A linear response to pressure is observed for the TM mode with a sensitivity of 0.0094 rad/kPa. This pressure sensor is rugged, is amenable to batch fabrication, and it provides a link-insensitive readout.>