Design of a passively mode-locking whispering-gallery-mode microlaser
Tomoki Suzuki, Ayata Nakashima, Keigo Nagashima, Rammaru Ishida, Riku Imamura, Shun Fujii, Sze Yun Set, Shinji Yamashita, Takasumi Tanabe
Abstract
Ultrahigh-repetition-rate lasers will become vital light sources for many future technologies; however, their realization is challenging because the cavity size must be minimized. Whispering-gallery-mode (WGM) microresonators are attractive for this purpose since they allow the strong light–matter interaction usually needed to enable mode locking. However, the optimum parameter ranges are entirely unknown since no experiments have yet been conducted. Here, we numerically investigate pulsed operation in a toroidal WGM microresonator with gain and saturable absorption (SA) to study the experimental feasibility. We show that dispersion is the key parameter for achieving passive mode locking in this system. Moreover, the design guideline provided in this work can apply to any small resonators with gain and SA and is not limited to a specific cavity system.