Fig. 1. Estimated thermal lens focal length of MgO∶PPLN crystal. (a) Thermal lens focal length caused by pump laser; (b) thermal lens focal length caused by signal laser; (c) thermal lens focal length caused by idler laser; (d) whole thermal lens focal length of MgO∶PPLN crystal

Fig. 2. Waist variation in resonant cavity

Fig. 3. Diagram of experimental setup

Fig. 4. Output power of signal and idler lasers versus incident pump power

Fig. 5. Beam quality analysis of 1550 nm laser

Fig. 6. Normalized intensity noise (RIN) spectrum of 1550 nm laser without PPKTP

Fig. 7. Output power of 1550 nm/775 nm laser versus incident pump power after adding PPKTP

Fig. 8. Power stability of signal laser (1550 nm), idler laser (3393 nm), and frequency-doubled laser (775 nm) within 5 h

Fig. 9. Single frequency characteristics of 1550 nm laser measured in experiment

Fig. 10. Beam quality analysis of 775 nm laser