Whispering-gallery wave

Summary

A whispering-gallery wave is a wave that travels around a concave curved surface while staying close to it. Examples are sound along the inside wall of a circular room and light along the rim of a glass sphere. In optics, a dielectric disk, ring or sphere supports whispering-gallery modes, light trapped near the rim by repeated total internal reflection. These modes have very large azimuthal mode numbers and can have extremely high quality factors. They are used in microresonators for lasers, sensors and frequency combs.