Controllable Brillouin laser and Brillouin-Kerr microcombs

Backward-stimulated Brillouin scattering (SBS) in microcavities has sparked interest in nonlinear optical physics and its associated applications. In this study, utilizing a hybrid microsphere cavity experimental platform, we showcase the remarkable tunability of thermal tuning in nonlinear SBS. We present a compact, low-cost, tunable cascade Brillouin laser source, demonstrating, for the first time, up to seven orders of cascade in SBS by varying the control power. Flexible switching of the Brillouin laser is achieved by changing the control power. Furthermore, the Brillouin-Kerr comb, generated by Brillouin-coupled four-wave mixing, also enables free switching of comb states. Specifically, soliton microcombs and microcombs with flat profiles are realized at specific control powers. This study on SBS boasts an ultra-high repetition rate and offers a novel solution for controlled Brillouin lasers and Brillouin-Kerr soliton microcombs, laying a new foundation for Brillouin laser spectroscopy and the utilization of Brillouin-Kerr soliton microcombs in related applications.