Fig. 1. Schematic diagram of pulsed single-frequency fiber MOPA

Fig. 2. Output power characteristics of fiber MOPA varying with active fiber length in main amplifier for pulse width of 2.4 ns and repetition rate of 20 kHz. (a) Maximum launched pump power; (b) maximum output peak power; (c) optical-to-optical efficiency

Fig. 3. Average power and peak power of fiber MOPA varying with launched pump power for pulse width of 2.4 ns and repetition rate of 20 kHz under different active fiber lengths in main amplifier

Fig. 4. Pulse waveforms. (a) Pulsed single-frequency laser seed; (b) main amplifier output at peak power of 91 kW

Fig. 5. Spectral linewidths. (a) Pulsed single-frequency laser seed; (b) main amplifier output at peak power of 91 kW

Fig. 6. Spectrum of main amplifier output at peak power of 91 kW and beam quality of pulsed single-frequency laser seed before and after amplification. (a) Laser spectrum; (b) beam quality of laser output after second cladding pre-amplifier; (c) beam quality of main amplifier output at peak power of 91 kW