High-power linearly-polarized single-frequency thulium-doped fiber master-oscillator power-amplifier

We report a high power narrow-linewidth source at similar to 2 mu m based on a Tm-doped fiber distributed-feedback master-oscillator and three Tm fiber amplifier stages. The master-oscillator and first two amplifier stages were in-band pumped by Er, Yb fiber lasers operating at 1565 nm, and the final stage amplifier was cladding-pumped at 795 nm by two spatially-combined diode-stacks. The MOPA yielded 100 W of single frequency output at 1943 nm with a beam propagation factor (M-2) of 1.25 and with a polarization extinction ratio of >94%. The output power was limited by thermally-induced damage in the final amplifier stage. The prospects for further power scaling are considered. (C) 2010 Optical Society of America