Simultaneous compensation of birefringence and thermal lensing effect in a high average power Nd:YAG amplifier

Thermally induced birefringence and thermal lensing in Nd:YAG rod amplifier was compensated by a 90° rotator with three sets of imaging optics. Experimentally, 2.8% single pass birefringence loss was achieved and a nearly diffraction limited amplified output was observed.