Reducing Temperature Effects in Optical Resonator Sensors

A differential-frequency measurement technique has been devised to reduce the spurious contributions of temperature fluctuations to determinations of physical quantities from readings of optical resonator and interferometric sensors. The technique is applicable mainly to sensors in the form of whispering-gallery mode (WGM) optical resonators. The evanescent electromagnetic fields of such resonators interact with their environments, such that their resonance frequencies change in response to environmental changes (e.g., a change in the index of refraction of the surrounding medium) that one seeks to measure. The resonance frequencies also vary significantly with temperature, with consequent introduction of errors and uncertainties and, hence, effective loss of sensitivity to changes in quantities other than temperature that one seeks to determine.