100-W-level monolithic single frequency Tm-doped fiber MOPA

We demonstrate a monolithic single-frequency Tm-doped fiber master oscillator power amplifier (MOPA) with output power of 102 W. A single-frequency fiber laser with linewidth of less than 100 kHz and central wavelength of 1.97 m was used as the seed laser of the MOPA. The main amplifiers slope efficiency was about 50%. Neither stimulated Brillouin scattering (SBS) nor other nonlinear effects were observed by monitoring the backward spectrum and power of the MOPA. The single-frequency output power could be further improved if more pump power can be launched into the MOPA.