57 mJ with 10 ns passively Q-switched diode pumped Nd:YAG laser using Cr4+:YAG crystal

In this paper, a side diode pumped passively Q-switched Nd:YAG laser is presented using a Cr4+:YAG as saturable absorber. The performance of the Nd:YAG laser in the free-running and Q-switched modes is theoretically and experimentally studied with different output coupler reflectivities and different initial transmissions of Cr4+:YAG crystals. The optimum reflectivity of the output coupler is found to be 25 % in the Q-switched mode according to the theoretical calculations and experimental results. The initial transmission of Cr4+:YAG is set to 20 % in order to achieve maximum output energy in a single laser pulse. The experimental results are in good agreement with calculated values. In the Q-switched mode, single pulse output energy is obtained around 57 mJ with 10 ns pulse duration over 1–20 Hz pulse repetition rates. The optical to optical conversion efficiency reaches 14.25 %.