热透镜控制激光光束质量技术研究

Controlling technique of beam quality by thermal lensing

在端面抽运固体激光器中,就如何改善在高抽运功率时输出激光的光束质量,提出一种激光器的设计方法。在激光器谐振腔中放入多根掺杂浓度不同的激光介质,利用激光介质内部产生的热透镜控制抽运光和基模振荡光的空间分布,并且最大限度地使抽运光的分布区和基模振荡光分布区重叠,实现抽运光与基模振荡光在空间上高度匹配,进而提高抽运光能量的利用效率和振荡光的光束质量。实验表明,在不同抽运功率下,抽运光和基模振荡光在晶体内部的光斑的空间分布可通过热透镜加以控制。在端面抽运功率200 W附近时,实现了抽运光与基模振荡光较高程度匹配,光束质量因子M2由14.7改善为4.1。

Aiming at improving laser beam quality in designing high power end-pumped Nd- YAG laser, thermal lensing effect is employed to achieve high beam quality in Nd：YAG laserin this paper by placing two more Nd ＂ YAG crystals with different doping concentrations in the resonator. Under action of pumping light, thermal lensing generated from the Nd ＂ YAG crystal is used to shape special distribution of pump beam and fundamental mode beam. Tighter overlapping of both beams results in higher efficiency of pump power and better beam quality of laser. Experimental results show special distribution of pump beam and fundamental mode beam can be shaped by thermal lensing effectively under different pump power. Two beams are matched closely at pump power of 200 W, and Mz is improved from 14.7 to 4.1.