Power scalability of a linearly-polarized narrowband random fiber laser in an all-fiber MOPA structure with 0.1 nm linewidth

In this manuscript, we demonstrate an all-fiberized master-oscillation-power-amplifier (MOPA) structured linearly-polarized narrowband random laser. The seed source is a narrowband random-polarized random fiber laser (RFL) in a half-opened cavity with a maximum output power of 0.981 W and a linewidth of 0.1 nm. Utilizing a polarization-dependent isolator as a polarizer, a linearly-polarized narrowband seed laser can be obtained. As for the main amplifier, a pump-limited 381.1 W amplified linearly-polarized narrowband random laser can be achieved with a linewidth of 0.13 nm (33.36 GHz) and a polarization degree of 92.33% (similar to 11 dB). The performance of the system is limited by the generation of mode instability (MI) effects, and hence, the worsening of temporal stability and the reduction of beam quality. Furthermore, significant tail broadening of the output spectrum can be measured. As the output and backward powers increase monotonously with the boosting of pump power, we conclude that further power scaling of this system with good linewidth, polarization, beam quality and temporal stability performance can be achieved with effective mitigation of the MI effect. This work can expand our comprehension on the spectral evolution property of RFL in the power scaling process and provide a possible solution for the obtaining of powerful linearly-polarized narrowband fiber source.