Characteristics of Cryogenically Cooled 946 nm Nd: YAG Laser Under 885 nm Direct Pumping

The characteristics of cryogenically cooled 946 nm Nd: YAG laser under 885 nm low quantum defect pumping are studied. The Boltzmann distribution fraction of the upper and lower laser levels as a function of temperature is introduced into the laser rate equation, and the change rule of small signal gain and laser threshold at low temperature is analyzed qualitatively. A cryogenic system is developed to study the output characteristics of the 946 nm laser at low temperature. A maximum 165 mW laser output with the slope efficiency 36% is achieved at 210 K. The slope efficiency is increased by 71 % compared with the room temperature operation. The gain of 1061 nm laser enhanced at low temperature is observed and analyzed. When the temperature is lower than 190 K, the gain of 1061 nm laser significantly increases and 1061 nm laser competes with 946 nm laser, resulting in a decrease of 946 nm laser output.