Whispering-Gallery Mode Lasers: A New Frontier in Micro resonators

Abstract

Whispering Gallery mode (WGM) optical microcavities represent a significant focus in current laser research. Initially, this paper elucidates the concept of WGM and its acoustic significance, before delving into its development in the optical field and its crucial role in optical devices. Subsequently, the author explores the theoretical foundations of WGM, elucidating the photon confinement effect due to total internal reflection. These optical microcavities are noted for their high symmetry and surface smoothness, which confer an exceptionally high Q-factor. The enhanced light-matter interactions in these microcavities lead to substantial improvements in nonlinear optical effects, laser gain, and photonic crystal effects within the amplified optical fields. The author discusses micro resonators, the fabrication methods of microcavities, and the unique nonlinear optical effects arising from high Q-factors and small mode volumes, including Stimulated Brillouin Scattering, Stimulated Raman Scattering, the Kerr effect, and four-wave mixing. These effects hold broad application prospects in fields such as precision spectroscopy, optical communication, and frequency comb generation. The advantages of WGM optical microcavities in laser fabrication and the study of nonlinear optical effects are summarized, with an outlook on their potential applications in future optical fields, such as high-sensitivity sensors and low-threshold lasers.