Interference pattern generation of optical third harmonic whispering gallery modes in microbubble resonators

Abstract

Static optical field interference pattern in whispering gallery mode resonators occurs when two or more modes have the same frequency. Here we report interference pattern generation of the optical third harmonic (TH) modes in microbubble resonators. We found that the interference patterns form via two paths, one is two degenerate fundamental modes generate two TH modes, both fundamental modes and TH modes form interference patterns. Meanwhile in the other path, only one fundamental mode is involved, in addition to the direct THG process that generates a TH mode, a secondary TH mode comes from opto-mechanical coupling assisted THG process. Therefore only TH modes form interference pattern. Our work extends the observation of interference pattern of whispering gallery modes to nonlinear optical fields.