Hz-level intrinsic linewidth Brillouin fiber laser in the visible range

We report on the development and characterization of a compact visible Brillouin fiber laser. The laser is designed in a short cavity configuration and demonstrates an output power of 30 mW. Detailed analysis reveals an intrinsic linewidth of 6 Hz, indicating exceptional spectral purity. Comprehensive gain characterization was performed as a function of pump power, providing critical insight into the laser's performance and limitations. These findings contribute to the advancement of compact, highly stable visible fiber lasers for quantum technologies and microwave photonics.