Q-switching of a diode-pumped Nd:YAG laser with low uniform gain characteristics

We have investigated Q-switching techniques in a low gain multi-transverse mode Nd: YAG laser. The laser rod is mounted in a solid prism, and diode-pumped so as to create a uniform gain distribution throughout the rod. We have obtained 10 mJ pulses with pulsewidths of less than 10 ns, from an incident diode energy of 115 mJ, scalable to 100 Hz pulse repetition rate. To obtain this performance, we have used a number of techniques to compensate for birefringence, including a DC bias on the LiNbO₃ Q-switch, or a quarter wave plate adjusted to compensate for the elasto-optic effect. Thermal birefringence in the laser rod has been reduced by actively cooling the prism. An alternative approach is to avoid overall birefringence losses by using a polariser which directs the rejected light back into the laser cavity.