High Average Power Q-switched Diode-Pumped Yb:YAG Laser

In Phase II we will develop a high brightness, high power, variable pulse repetition rate diode-pumped Yb:YAG laser suitable for military applications including target illumination from airborne or other mobile platforms. Utilizing an innovative near-grazing total internal reflection (TIR) resonator configuration and a composite laser crystal, over 150 to 220W of Q-switched average power at 2 to 10 kHz, high overall efficiency (>25% optical) and excellent beam quality (TEM00 mode) will be obtained in a very compact laser system. Our Phase I work has successfully demonstrated a novel multi-pass direct side diode pumping scheme providing >95% pump coupling with a low Yb doped crystal. A bread-board side pumped Yb:YAG laser was constructed for demonstrating the feasibility of our approach and for measurements of laser performance, thermal lensing and thermal loading in the crystal. Good experimental results: high laser slope efficiency 30% with non-optimal QCW pumping, low thermal loading 12.8% (even in non-lasing condition), and excellent agreement with predictions from our analytical laser model were obtained. A full power prototype laser with a novel double gain module configuration that minimizes thermal lensing, to ensure excellent beam quality (M2 < 1.1) essential for high brightness output, will be built in Phase II and tested.