406 W Narrow-Linewidth All-Fiber Amplifier With Tm-Doped Fiber Fabricated by MCVD

A homemade 25/400 thulium-doped silica fiber for high power laser and an all-fiber bi-direction pumped thulium-doped master-oscillator power-amplifier (MOPA) configuration with output power of 406 W are presented. The concentration of Tm
₂
O
₃
and Al
₂
O
₃
was set as 2.6 wt.% and 1.01 wt.% respectively. Cladding Absorption at 793 nm was measured to be 3 dB/m. The output power of 406 W was obtained by improving coating stripping of splice for thermal management, corresponding to slope efficiency of 54%. The 3 dB spectral linewidth was narrow as 84 pm. Neither amplified spontaneous emission (ASE) nor non-linear effect was observed and the output power only limited by pump power.