Resonant frequency control of a microspherical cavity by temperature adjustment

We demonstrate frequency tuning of whispering-gallery mode resonances in a fused-silica microsphere by means of temperature control. Scattering spectra of the microsphere are measured using a tunable narrow-linewidth diode laser, and the frequency scale is precisely calibrated from a simultaneously observed spectrum of rubidium vapor. The resonant frequencies of whispering-gallery modes can be varied linearly by temperature elevation and lowering, at a rate of -2.6 GHz/K for a 190 mum sphere.