Q-switched operation of dual-cavity Nd:YAG lasers

We report Q-switched operation of a dual-cavity Nd:YAG laser with a fundamental Gaussian TEM 00 mode, a first-order Laguerre–Gaussian mode, or a multimode, which can be selected simply by adjusting the apertures in the primary and secondary cavities. By exploiting an acousto-optic modulator, the laser produced Q-switched pulses of a pulse energy of 146 μJ with a pulse duration of 101 ns at a repetition rate of 1 kHz in the TEM 00 mode, 140 μJ with a pulse duration of 102 ns in the LG 01 mode, and 160 μJ with a pulse duration of 98 ns in the multimode. A simple analytical expression for the overlap efficiency of the LG 01 mode in the dual-cavity resonator is also derived, showing that the calculated result is in very good agreement with the experimental value. The prospects of further improvement in the dual-cavity laser with tunable laser beam profiles are discussed.