Effect of Pump Beam Shape on Thermal and Stress Distribution within the Laser Crystal in Diode Pumped Solid-State Lasers

Abstract

Thermal effects formed in a solid-state laser crystal, which cause the appearance of thermal lensing، mechanical stress and birefringence, lead to laser beam distortion and shorten the lifetime of laser crystal، and hinder getting a high-quality laser beam, even when using diode end-pumped solid-state lasers. In this work, the thermal effects in two types of end-pumped solid state lasers namely Nd:YAG and Nd:KGW have been investigated. In this study, the finite element method (FEM) was used to calculate thermal and stress distribution within end pumped laser crystals. The calculations carried out for different power of 5، 10 and 15 Watt and different pump beam shapes: first a Gaussian beam، second super Gaussian and last a Top Hat beam. The results were compared to experimental and theoretical values from previous studies. We also calculated the focal length of thermal lens and compared the results to an experimental measurement for one case of Nd:KGW Laser. The obtained results are useful in designing diode end-pumped solid-state lasers and in evaluating and mitigating thermal effects within laser crystals, which is important to improve laser performance and beam quality. The results are also useful in evaluating stress intensity resulting from thermal distribution gradient within the laser-generating crystal, to prevent cracks, bulges or crystal damage.

Keywords

• nd:yag، nd:kgw، laser diode، end-pumped، thermal lensing، mechanical stress.