Review of different coupling methods with whispering gallery mode resonator cavities for sensing

Abstract

Whispering gallery mode (WGM) resonantors are famous for high-quality factor, low loss, small size, and low sample requirement. A considerable sensor application has grown up around the theme of it. The coupling of light has long been a question of great interest in various fields, such as sensors, low-threshold lasers, and optical filters. WGM microcavities based on various coupling methods have received considerable attention. In a WGM coupling system, different coupling methods will largely determine the sensitivity and application area of a sensor. This paper briefly reviews several coupling methods related to WGM and introduces their applications. It is hoped that this research will contribute to a clearer understanding of the coupling methods.