High-Power, Narrow-Linewidth, Continuous-Wave, Thulium-Doped Fiber Laser Based on MOPA

A high-power, narrow-linewidth, continuous-wave, thulium-doped fiber laser (TDFL) based on a master-oscillator power-amplifier (MOPA) was experimentally demonstrated. The main oscillator (seed source) yielded 0.64 W of narrow-linewidth laser output at a central wavelength of 1940.32 nm and a 3 dB spectral bandwidth of 0.05 nm. The output narrow-linewidth laser from the main oscillator was amplified by two-stage, cladding-pumped, thulium-doped, all-fiber amplifiers. The main amplifier yielded 26 W of narrow-linewidth laser at a central wavelength of 1940.33 nm. The slope efficiency of the main amplifier was approximately 55.6%. Significant residual pumping light component in the output laser was not observed. During the amplification process, no stimulated Brillouin scattering (SBS) effect, strong amplified spontaneous emission (ASE) effect, and parasitic lasers were observed at the reverse monitoring end. Moreover, the output power was only limited by the incident pump power and the output power had a good stability in a 50 min monitoring period.