采用正支虚共焦非稳腔对非链式脉冲HF激光谐振腔进行了优化,提高了激光光束质量。采用不同放大倍率和不同模体积直径,设计了5种不同参数的激光谐振腔。利用聚焦法测量了焦面远场光斑,采用衍射极限倍数法分析了激光光束质量变化规律,比较了不同腔参数激光脉冲能量的变化规律。实验结果表明,非稳腔放大倍率大于2.5倍情况下,可以得到约2.3倍衍射极限的激光输出。为了得到较好的实验结果,在实验所用的放电电极结构下,激光模体积直径控制在增益区截面直径的80%以内情况下得到的光束质量较好。 The unbranched confocal resonator with positive branch was used to optimize the non-chain pulsed HF laser cavity and improve the laser beam quality. Five kinds of laser cavity with different parameters were designed by using different magnifications and different module volume diameters. The focal spot far-field flare was measured by focusing method. The law of laser beam quality was analyzed by diffraction limit multiples method. The variation of laser pulse energy in different cavity parameters was compared. The experimental results show that the laser output of about 2.3 times the diffraction limit can be obtained under the condition that the magnification of unstable cavity is more than 2.5 times. In order to get better experimental results, under the structure of the discharge electrode used in the experiment, the laser beam with the volume diameter controlled within 80% of the diameter of the gain section is better.