A 621 W linearly polarized, near-diffraction-limited MOPA seeded by random fiber laser

We demonstrate a high-power linearly polarized random fiber laser (RFL) based on master oscillator power amplifier (MOPA) configuration. The maximum output power of 621 W is obtained with conversion efficiency of 73.6 %. Near-diffraction-limited beam quality and high polarization degree of 93.9 % are obtained at the maximum output power. To the best of our knowledge, this is the highest output power of linearly polarized RFL for the time being, which proves the feasibility of high-power linearly polarized RFL. Further power scaling is limited by the mode instability (MI) at present, and will be realized if effective MI-mitigation strategies are introduced in the future work.