Abstract: Due to its excellent characteristics of good beam quality, narrow pulse width and compact structure, all-solid-state passively Q-switched lasers have a wide application in radar detection, industrial manufacturing etc. Here, the output characteristics of passively Q-switched YAG/Nd: YAG/Cr4+ : YAG laser are studied theoretically and experimentally. While being pumped by 808 nm laser with 230 μm beam diameter and 6.72 W power, a Q-switched laser output with an average power of 1.41 W and pulse width of 736 ps at the repetition rate of 8.46 kHz is obtained. Furthermore, it is shown that the symmetry of the laser beam decreases as the focus of the pump laser moves away from the Nd: YAG end face, and the laser threshold shows an upward trend when the distance between the focus of the pump laser and the Nd: YAG end face increases along the axis of the crystal.

Key words: laser techniques, all-solid-state, composite crystal, passively Q-switched, Cr4+: YAG