Fig. 1. Schematic diagram of 2-μm high power fiber laser. LD: laser diode; CPS: cladding power stripper; EFC: endcaped fiber cable

Fig. 2. Physical diagrams of the seed source and amplification stage of the 2-μm high-power laser

Fig. 3. Spectrogram of the seed laser

Fig. 4. Output characteristics of seed laser

Fig. 5. Spectram of MOPA laser at different output powers

Fig. 6. Output characteristics of MOPA laser before and after optimization

Fig. 7. Output power and conversion efficiency of the MOPA laser versus the pump power after turning on 4 pumps in the amplified stage

Fig. 8. Laser output power versus the duty cycle under different modulation frequencies

Fig. 9. Pulses with 50 Hz repetition rate and 1 ms pulse width