Fig. 1. Diagram of experimental setup of SHG by double crystal cascade

Fig. 2. SHG power and efficiency of double crystal SHG structure

Fig. 3. Normalized SHG efficiency as a function of distance between two crystals

Fig. 4. Comparison of SHG with double crystal and single crystal. (a) Output power; (b) efficiency of SHG

Fig. 5. Quasi-phase matching temperature

Fig. 6. Phase matching temperature bandwidth of MgO∶PPLN crystal

Fig. 7. Beat frequency of SHG laser

Fig. 8. Beat frequency of green laser. (a) Beat frequency stability of 150 MHz; (b) beat frequency stability of 300 MHz