High-power Nd : YAG laser with birefringence compensation and adaptive HR-mirror

In this article we describe an efficient method of the compensation of ther mally induced birefringence in high-power Nd :YAG rod lasers. Losses at a r esonator internal polarizer due to depolarization in the rods are reduced, and a polarized cw laser with an output power of 300 W is realized. Resonat ors with a small stability range and therefore beam quality near the diffra ction limit are introduced. To improve the variability and stability of suc h resonators, an adaptive high reflecting mirror is used as resonator mirro r. The maximum average output power of the resonator with adaptive mirror i s 145 W at a beam quality of M-2 congruent to 2.