Abstract:

Whispering Gallery Mode (WGM) microcavity lasers have gained widespread attention in multiple research fields due to their advantages of small mode volume, ultrahigh Q value, and low threshold. However, WGM microcavity lasers suffer from poor laser directionality, making the emission angle difficult to control. They may also be accompanied by multi-longitudinal-mode laser radiation, which significantly limits their practical applications. This paper systematically reviews the research dynamics in the field of WGM laser directional emission control. It focuses on four core control mechanisms: deformed microcavity design, scattering bodies and defect assistance, coupled microcavity systems, grating induction, and PT symmetry breaking. By deeply analyzing their working principles and making forward-looking predictions about the technological evolution trends in this field, this paper aims to provide theoretical support for researchers in related fields and promote the technological innovation of WGM laser directional emission mechanisms.

Key words: WGM microcavity, directional emission, deformed microcavity, PT symmetry