Optical micro-resonator sensor for air velocity measurement

Abstract

The proposed sensor utilizes a whispering gallery mode (WGM) resonator to measure velocity-induced non-coherent Doppler shifts in Mie-scattered light from particles moving with the air-flow. The resonator replaces the typical Fabry-Perot instrument to measure the Doppler shift. A prototype sensor was developed and experiments were carried out in an atomizing nozzle with a 25μm-diameter water-droplet-seeded air jet. Individual velocity measurements were made at the center of the nozzle, switching the flow on and off. Preliminary results show promise for the WGM-based velocity sensor concept, which would significantly reduce the size and weight of future Direct-Detection-Doppler systems for air-speed measurement, with possible applications in airborne-platform weather-monitoring and planetary studies.