High power Yb-Raman combined nonlinear fiber amplifier.

We demonstrated a high power Yb-Raman combined nonlinear fiber amplifier. The seed is a 30 W dual-wavelength Yb-doped fiber laser formed by 1070 nm and 1120 nm lasers. The gain medium in the amplifier stage is a 45-meters-long Yb-doped fiber, which power scaled the 1070 nm laser and Raman amplified the 1120 nm laser simultaneously. A record 1120 nm power of 732 W is obtained with pump power of 890 W. Numerical study taking into account of both Yb and Raman gain has been conducted to analyze the output characters and power evolution in the amplifier under different conditions. The numerical results are in good agreement with the experiment. This amplifier is also suitable to amplify laser in the wavelength range of 1100-1150 nm.