Whispering gallery mode resonance transfer in hollow microcavities

We investigated the hollow whispering gallery mode (WGM) microcavity, in which the WGM resonance position is transferred when n_core = n_wall (referred to as a “jump point”). Via numerical simulation, we verified the WGM resonance trajectory from the wall to the core with changes in the core refractive index from n_core < n_wall to n_core > n_wall. Owing to the transfer of the WGM resonance characteristics, the refractive-index sensitivity, Q value, and free spectral range of the WGM resonance differed markedly after the jump point. This study can be considered as a proof of concept and can be extended to higher-quality microspheres or microbubbles.