310-W Single Frequency Tm-Doped All-Fiber MOPA

We present a high-power single frequency (SF) Tm-doped fiber amplifier employing all-fiber master oscillator power amplifier (MOPA) configuration. An SF fiber laser with ultrashort cavity and output power of ~40 mW was used as the seed laser of the MOPA, and the central wavelength located at ~1971 nm. The final output power of the MOPA reaches 310 W with slope efficiency of 0.56, and no amplified spontaneous emission or parasitic lasing is observed. The stimulated Brillouin scattering threshold is not reached yet, and the output power is only pump limited. This is the first demonstration, to the best of our knowledge, on an SF Tm-doped all-fiber MOPA with output power exceeding 300 W.