Study of acousto-optic Q-switched green laser with high efficiency, high stability and high-quality coherent beam generation

High-power and high efficient coherent beam generation with good green-beam quality has been achieved by optimizing the diode-side-pumped linear cavity geometry with two modules in tandem, acousto-optic Q-switching and with S-KTP of II-type phase-matching for intracavity frequency doubling of a Nd:YAG laser. When the pump current is 45A, the maximum average green output power of 132 W is obtained with pulse width of 120 ns at pulse repetition rate of 15 kHz, corresponding to the conversion efficiency of 13.2% from diode pump power to green output power. The M² beam quality factor is 6.7 at output power of 130 W, and the output power instability is less than 0.5% at the same output power during an hour measurement time. The thermo-lensing effect of the laser medium and the stable region of the laser cavity under high power pumping are also theoretically analyzed and experimentally researched.