Fig. 1. Nd∶YAG level structure

Fig. 2. Variation of laser threshold or gain with temperature at low temperature

Fig. 3. Experimental setup for cryogenic Nd∶YAG 946 nm laser system

Fig. 4. (a) Output power of 946 nm laser at different crystal temperatures when absorbed pumping power is 750 mW; (b) variations of output power of 946 nm laser with absorbed pumping power at different crystal temperatures

Fig. 5. (a) Pulse trains of LD pumping and laser; (b) single pulse profile of LD pumping and laser at 280 K;(c) single pulse profile of LD pumping and laser at 210 K

Fig. 6. 946 nm laser beam quality at low temperature

Fig. 7. Spectra of laser at different crystal temperatures. (a) Higher than 190 K; (b) in the range of 190-180 K; (c) below 180 K