Study of a High-Power, Long-Pulse-Width Acousto-Optical Q-Switched 1064 nm Laser Based on a Multi-Pass Cavity

A high-power, long-pulse-width acousto-optical Q-switched 1064 nm laser based on a multi-pass cavity (MPC) is reported in this paper. First, a plano-concave MPC structure satisfying the Q-preserving configuration was designed and introduced into an acousto-optical Q-switched plano-plano cavity Nd:YAG laser, extending the original laser cavity length by 1200 mm. The laser achieved a maximum average output power of 123.6 W with a repetition rate of 10 kHz. At this power level, the laser pulse width was broadened to 157.5 ns, which can be compared to 82.5 ns without the MPC structure, achieving a broadening ratio of 90.9%. The beam quality factors were Mx2 = 10.75 in the horizontal direction and My2 = 11.37 in the vertical direction. The experimental results demonstrate that inserting an MPC into the cavity is an effective method for broadening the pulse width of nanosecond lasers.