Temperature influence on microchip lasers based on Nd:YAG crystal

The influence of temperature (from 80 up to 400 K) on emission of microchip lasers based on Nd:YAG crystal together with its spectroscopic properties was investigated. Three microchip lasers primarily designed for emission at 1.06, 1.32, and 1.44 μm, were tested. For all three lasers, the same parameters of Nd:YAG rod were used (Nd-doping » 0:9 at.% Nd/Y, length of 5 mm, diameter 5 mm). Resonator mirrors were deposited directly on the laser crystal faces. The output coupler transmission for desired wavelength was 2-5 %. The microchip lasers were placed in the temperature controlled cupreous holder inside vacuum chamber of the liquid nitrogen cryostat. The lasers were longitudinaly pumped by 808nm fibre-coupled pulsed laser diode (pulse duration 10 ms, repetition rate 10 Hz, maximum pumping power amplitude 10.5 W). The output microchip laser emission wavelength, laser threshold, laser slope efficiency, and laser beam profile were measured in temperature range from 80 up to 400 K. It was found that temperature strongly influenced mainly the laser beam profile and divergence which is rising with temperature (about 120% per 100 K). There exists also a significant influence on laser emission wavelength. Rich set of laser emission lines were obtained with these three lasers: 1061 and 1064nm (1.06 μm laser), 1318, 1332, 1338, and 1354nm (1.32 μm laser), and 1354, 1412, and 1444nm (1.44 μm laser). Generally, a higher temperature caused a longer emission wavelength. The temperature influence on lasers input-output characteristics was not so strong. For all three samples the best results were obtained for temperature in range 200-250 K. The highest laser slope and lowest threshold power were following: 60% and 0.8W (1.06 μm laser), 44% and 1.2W (1.06 μm laser), and 16% and 1.7W (1.44 μm laser).