Frequency locking for asymmetric Mach-Zehnder interferometer coupler-based Brillouin lasers

As essential components in inertial navigation, Brillouin fiber-optic gyroscopes (BFOGs) still suffer from low coupling efficiency, complex frequency locking, and large size. This paper presents an asymmetric Mach-Zehnder interferometer coupler (AMZIC)-based resonator to address these challenges. A dedicated frequency-locking scheme is proposed for the distinctive butterfly-shaped Brillouin spectrum. Experimental results demonstrate a low threshold of 27.44 mW, a short resonator (5.9 m), and a polarization extinction ratio of 31 dB. Stable frequency locking was maintained over 4000 s, confirming the system's robustness and potential for practical BFOG applications.