Fig. 1. Experimental setup. (a) Laser oscillator; (b) Yb-doped fiber amplifiers and AOM; (c) master oscillator power amplifier; (d) SHG device

Fig. 2. Experimental results. (a) Pumping efficiency curves of HP-LD; (b) spectra of fundamental frequency laser corresponding to different repetition frequencies; (c) pulse width of fundamental frequency laser at 20 MHz; (d) SHG power efficiency conversion curves; (e) SHG spectra at different repetition frequencies; (f) SHG pulse width at 20 MHz

Fig. 3. Effect of crystal temperature on frequency doubling and SHG power stability. (a) Relationship between SHG power and crystal temperature at different repetition frequencies of fundamental frequency laser; (b) spectra of SHG laser at 20 MHz at different temperatures; (c) SHG power stability and facula (inset)