Watt-level, widely tunable 1.5-μm Brillouin fiber laser with low intensity and frequency noise

Achieving watt-level output power, broad wavelength tunability, and comprehensive noise suppression simultaneously remains challenging for Brillouin fiber lasers (BFLs) due to trade-offs among these performance metrics. Here, we demonstrate an all-polarization-maintaining (all-PM) passive BFL pumped by a high-power, widely tunable master oscillator power amplifier (MOPA) source at 1.5 μ m . Across the measured operating wavelengths from 1535 to 1570 nm, the laser maintains an output power of at least 1.53 W and an optical signal-to-noise ratio exceeding 80 dB, with short-delay self-heterodyne linewidth estimates below 1.1 kHz. At 1550 nm, the BFL suppresses the pump relative intensity noise (RIN), approaching the calculated shot-noise level at high frequencies, while frequency-noise measurements yield an inferred fundamental linewidth of approximately 0.72 kHz and an integrated linewidth of approximately 7.3 kHz at a 1 ms observation time. Low RIN is also observed over the measured wavelength span. The all-PM cavity eliminates polarization-induced gain fluctuations, thereby favoring effective SBS gain utilization and enabling high-power operation without the need for polarization adjustment. The demonstrated combination of power, wavelength coverage, and noise performance makes this passive all-PM BFL attractive for nonlinear and quantum optics applications.