High-power short-wavelength Tm-doped fiber amplifier at 1907nm with angle-cleaved fusion splicing

An all-fiber high-power short-wavelength Tm-doped fiber (TDF) master oscillator power amplifier (MOPA) at 1907nm is presented. The master oscillator is a linear cavity structure that provides a 34.6 W signal light power to the amplifier. In the power amplifier, a method of combining angle-cleaved fusion splicing and gain fiber length cutting has been proved the feasibility for suppressing the parasitic oscillation and improving the output power of the 1907nm laser. By shortening the amplifier gain fiber length to 4 m and fusing the gain fiber at a 5° angle, a maximum output power of 753.1 W at 1907nm with high spectral purity is obtained with a corresponding slope efficiency of 57.7% and optical to optical conversion efficiency of 51.3%. The spatial quality factor and power stability of the TDF MOPA system are 1.60 and 0.1% @ 20 min, respectively. This angle-cleaved fusion splicing method has the potential for mitigating parasitic oscillation in the 1907nm high-power Tm-doped all-fiber MOPA system.