为了优化高功率板条激光器的光束质量, 采用提高单侧基模光束的尺寸来限制腔内部分高阶模式振荡的方法,针对半导体侧面抽运板条激光器, 测量了激光器在抽运状态下水平和竖直方向热焦距, 建立了热透镜等效模型, 并以平-平腔为参考, 设计了水平和竖直方向单侧基模尺寸均会扩大的平-凹腔。验证了对于激光介质截面尺寸固定的板条激光器, 扩大单侧基模尺寸可以限制高阶模式从而优化光束质量, 并提出了进一步优化板条激光器性能的研究方法。结果表明, 当平-凹腔的腔长为370mm时, 输出功率为59.9W, 水平方向M2因子由平-平腔的115.6显著优化至32.9, 竖直方向M2因子由116.4显著优化为60.9。该研究对于板条激光器获得高质量输出及相关应用有实际意义。

In order to optimize beam quality of high power slab lasers, the oscillation of some high-order modes in the cavity was limited by increasing the size of unilateral fundamental mode beam. For semiconductor side-pumped slab lasers, horizontal and vertical thermal focal lengths of the laser under pumping were measured. The equivalent model of thermal lens was established. By using flat-flat cavity as reference, a flat-concave cavity with enlarged dimension of unilateral fundamental modes in both horizontal and vertical directions was designed. It was verified that, for slab lasers with fixed cross-section size of laser medium, expanding the size of one-sided fundamental mode can limit the higher-order mode and optimize the beam quality. A method for further optimizing the performance of slab lasers was proposed. The results show that, when the length of flat-concave cavity is 370mm and the output power is 59.9W, horizontal M2 factor is significantly optimized from 115.6 for flat-flat cavity to 32.9 and vertical M2 factor is significantly optimized from 116.4 to 60.9. This research has practical significance for obtaining high quality output of slab lasers and the related application.