75 W single-frequency, thulium-doped fiber laser at 2.05µm

We demonstrated a high-power, single-frequency (SF), all-fiber-format, thulium-doped master oscillator power amplifier (MOPA) system. The MOPA is seeded by a distributed feedback (DFB) diode laser and yields 75 W of SF laser output at a central wavelength of 2050.5 nm with a linewidth of 1 MHz. There is no indication of stimulated Brillouin scattering or gain saturation observed at the maximum output power, which means the output power was only limited by the available pump power. This is the highest output power, to the best of our knowledge, in the SF all-fiber thulium-doped MOPA at 2050 nm.