Fig. 1. (a) Schematic representation of the amplification process of the 1064 nm pump source. (b) Experimental setup diagram of the 1645 nm KTA-OPO.

Fig. 2. Pump beam waist spot for the 1064 nm pump light.

Fig. 3. Optical design of the OPO process.

Fig. 4. (a) Variation of the 1645 nm power with the pump power at 10 kHz, (b) variation of the 1645 nm power with the pump power at 9 kHz, and (c) variation of the 1645 nm power with the pump power at 8 kHz.

Fig. 5. Power stability of the 1645 nm signal light and the 1064 nm pump light.

Fig. 6. (a) Thermal imager observation of the temperature of the KTA crystals at T = 0 min. (b) Thermal imager observation of the temperature of the KTA crystals at T = 60 min.

Fig. 7. (a) Pulse duration of the 1645 nm signal light. (b) 10 kHz repetition rate of the 1645 nm signal light.

Fig. 8. Spectrogram of the 1645 nm laser spectrum measured by a YOKOGAWA spectrometer.

Fig. 9. Relationship between the rotation angle and the tuning wavelength of the KTA crystal.

Fig. 10. Near-field spot of the 1645 nm signal light.

Fig. 11. Beam quality factor of the 1645 nm signal beam measured by the Spiricon M2-200 s.