Feasibility of passive gas sensor based on Whispering Gallery Modes and its Radar interrogation: theoretical and experimental investigations

International audienceFeasibility of gas sensors based on Titanium Dioxide (TiO2) dielectric resonator operating with whispering-gallery modes is presented. The gas or humidity adsorption modifies the TiO2 dielectric permittivity and such modification induces variation in the resonant frequencies of high-Q whispering-gallery modes in the millimeter-wave frequency range. Full-wave electromagnetic simulation indicates that the measurement of this variation allows the derivation of few pars-per-million fluctuations in gas or humidity concentration. For validation purposes very first prototypes of resonator operating with whispering-gallery modes in the millimeter-wave frequency range are micro-machined. The obtained measured performances confirm that such high-Q resonant modes are very sensitive to small variations in dielectric resonator permittivity. Moreover we validate experimentally that these small variations can be remotely detected from the RADAR interrogation of an antenna loaded by the whispering-gallery modes resonator