A Tunable Whispering-Gallery-Mode Bottle Resonator

Whispering-gallery-mode (WGM) resonators, i.e., monolithic structures in which light is confined by continuous total internal reflection, offer a row of desirable properties. They realize the highest Q values for optical resonators to date. In addition, their relatively small mode volume of V ~1000¿
³
, where ¿ is the optical wavelength, allows to reach a high intra-cavity intensity for a small total energy stored in the resonator. This makes them ideally suited for applications in nonlinear optics as well as in cavity quantum electrodynamics. However, the tunability of all common WGM resonator types, like microspheres and -tori, was so far limited to less than one free spectral range.