Fig. 1. Distribution of central temperature at the end face of PPLN crystal under different spot pumping

Fig. 2. Temperature curve of crystal cross-sectional under different pump spots

Fig. 3. Thermal focal lengths at different incident pump spots

Fig. 4. Comparison of temperature tuning curves considering thermal effects. Insert: signal wavelength

Fig. 5. Schematic diagram of the experimental optical path

Fig. 6. Relationship between R₂ reflectance and optimal pump superthreshold multiple

Fig. 7. Relationship between conversion efficiency and pump light intensity under different crystal lengths

Fig. 8. Optical output power and optical-optical conversion efficiency of the signal change with the pump power at the repetition rate of 15 kHz

Fig. 9. Comparison of experimental results with temperature tuning curve. Insert: signal wavelength