1.55 μm High-Power Narrow-Linewidth Random Fiber Laser Emitted From a Standard Single-Mode Fiber

Spectral broadening and higher-order mode excitation are the two critical impediments to achieving high-power narrow-linewidth fiber lasing with exceptional beam quality. Even for random fiber lasers (RFLs), which have a unique advantage in achieving low relative intensity fluctuation, the accumulated nonlinear effects during the power-scaling process will still induce significant spectral broadening, especially for the spectral pedestal. Besides, the aggravation of higher-order mode excitation can further destroy the single transverse mode characteristic and beam quality of the laser. Here, by analyzing the spectral deviation-dependent temporal characteristics of a traditional active gain based RFL, we propose an effective strategy to address the above limitations: a narrow-linewidth Fabry-Pérot (FP) filter is integrated to eliminate the broadened spectral components, and additional power amplifiers are used to boost the power of the screened narrow-linewidth lasing components. Meanwhile, a customized mode field adapter (MFA) is specially introduced to suppress the higher-order mode excitation, and then re-converge the high-power laser beam to a standard single-mode fiber (SMF), thus ensuring the stable output of pure single transverse mode under high-power output conditions. As a result, a maximum output power of 80.5 W is achieved for the 1.55 μm band RFL, accompanying the simultaneous realization of narrow-linewidth, pure single transverse mode, and high-power output. This work provides a competitive lasing strategy to simultaneously gather narrow-linewidth, single transverse mode, and high-power lasing together, which exhibits great practical application potential in advanced laser pumping, spatial light modulation, and other high-performance laser source demand scenarios.