Fiber Brillouin lasers with ultralow frequency noise within wideband noise spectrum

The simultaneous suppression of both low- and high-frequency noise presents a critical challenge in the development of ultra-low-noise lasers. This work reports on a pump-locked, short-cavity fiber Brillouin laser that effectively addresses this issue by precisely controlling Brillouin gain detuning and cavity Q-factor. These parameters can be accurately determined and controlled by analyzing the profile of the fiber cavity mode spectrum. The optimized laser enhances slope efficiency to 90% and suppresses cascaded Brillouin scattering, enabling a 13.25 mW output power and an exceptionally low frequency noise level of 1 Hz²/Hz over a wide bandwidth (100 Hz-1 MHz). Furthermore, the pump-locking mechanism facilitates 110 MHz of continuous, mode-hop-free frequency scanning. This research establishes a robust, all-fiber platform for applications requiring ultra-low-noise laser sources.