Experimental and theoretical analysis of passively Q-switched lasers with a high output coupling

Abstract

In this work, a passively Q-switched Nd:YAG laser resonator, with an output coupling of more than 90%, was demonstrated. Laser pulse energy, peak power and pulse width were found to increase with the increasing of dissipative loss of the laser resonator, and pulse energy was found to increase from 38.6 mJ to 113 mJ, which almost meant a 200% increase. However, according to previous theoretical analyses of passively Q-switched lasers, pulse energy and peak power would decrease with the increasing of dissipative loss when the second threshold was satisfied, and a giant Q-switched laser pulse would never occur if the second threshold was not satisfied. For the passively Q-switched laser resonator we established, the second threshold was found not to be satisfied because of the high output coupling. So, we modified the solutions of coupled rate equations when the second threshold was not satisfied. Numerical calculation results were carried out, and these calculation results were basically consistent with the experimental results and previous investigations.