Micro resonator stabilization by thin film coating

In this paper we propose a method to overcome one the major fundamental limitation of silica spherical micro resonators for frequency reference, i.e. temperature stabilization, by coating the micro resonator with an appropriate material through the use of an innovative sol-gel method. We experimentally characterize the thermal drift of a resonant frequency of a silica microsphere coated by a Polymethyl Methacrylate (PMMA) thin film. By increasing the film thickness we demonstrated that the thermal drift can be largely reduced since the thermo-optic effect of the silica is compensated by the PMMA thin film.