Beam stability improvement of high-power Lissajous modes by an off-axis pumped YVO4/Nd:YVO4 laser

Abstract

Thermally induced beam deformation of Lissajous structured modes generated by an off-axis pumped solid-state laser with a uniformly -doped Nd:YVO4 crystal and a composite YVO4/Nd:YVO4 crystal is systematically explored. With the undoped front segment as an effective heat spreader to mitigate the thermal effects, a significant improvement on beam structure stability during power scaling can be found in experimental patterns of Lissajous modes by the composite crystal. By analyzing the deformed mode structures with the increasing pump level, it can be obviously seen that not only the thermal lensing effect can be greatly reduced to be less than half of the level by the uniform crysta,l but also the stress-induced beam rotation and elongation can be effectively alleviated via the YVO4/Nd:YVO4 crystal. Moreover, the output power performance for Lissajous modes by the composite crystal also exhibit a prominent upgrade for the overall slope efficiency to be 8% higher than the case by the uniform crystal. This demonstration may provide a potential solution for generating more stable high-order structured beams by the selectively pumped high-power lasers.