High-power single transverse mode random fiber laser based on the coherent feedback.

Realizing a high-performance random fiber laser (RFL) in a compact structure is still challenging to the laser optics field. Here, we propose a ~1.5-μm band high-power single transverse mode coherent feedback RFL in a single-stage structure. A scattering-enhanced structure composed of large-scale random-distributed fiber Bragg gratings (RD-FBGs) is fabricated to provide the coherent feedback. The enhanced random feedback degree of freedom of the RD-FBG array can greatly restrict the nonlinear accumulation, leading to significant spectral broadening during power boosting and mitigating coherent mode competitions. The maximum output power larger than 13 W is obtained, while its 3 dB and 20 dB bandwidths remain only ~0.1 and ~0.5 nm, respectively. The large-scale RD-FBG array greatly enhances the scattering efficiency in a compact structure (e.g., ~81 m), which provides a competitive alternative for high-performance random lasing.