Wavefront Compensation of Zig-zag Slab Laser Amplifier under High Power Diode Laser Pumping

A diode-pumped Nd:glass zig-zag slab laser was developed for the purpose of inertial fusion energy (IFE) driver and material processing. In this laser system, we obtained 10.6 J output at 1 Hz repetition rate and 8.4 J at 10 Hz [1]. As a repetition rate increased, the obtainable output energy was limited because of thermal lensing of laser glass induced by high average power laser diode pumping. Uniform pumping technique [2] on the laser glass was developed to minimize thermal lensing. However, additional thermal management of slab edges needed to be done. In this paper, we examine the slab structure that affects temperature distribution in the laser glass. We found that the boundary layer between the laser glass and the slab holder absorbs spontaneous emission. We demonstrate that the optimization of the boundary layer allows the amplified laser beam to propagate the optical system properly without significant thermal lens effect. As a result, the obtained energy has been increased 30% compared to without optimization.