光学元件“缺陷”对助推放大级光束质量的影响

 光学元件“缺陷”制约着高功率固体激光装置负载能力的提升。从统计角度建立了振幅调制型“缺陷”模型，并针对神光Ⅲ原型装置助推放大级分析了“缺陷”分布的统计参量与光束近场质量的关系，得到了一般规律。结果表明，“缺陷”总密度的增加和幂指数的减小都使系统输出光强的中高频成分增加，光束近场质量变差；总密度的变化引起光强各中高频成分变化的幅度近似相等，频率间相对比重基本保持不变，幂指数的变化却会引起各频率间相对比重发生变化；一定范围内，“缺陷”尺寸越大对近场质量的影响越严重；对于助推段，需将元件的“缺陷”总密度控制在600 cm^-2以下，幂指数控制在2.5以上。研究结果可为降低元件的损伤风险以提高系统的运行负载提供参考。

Effects on beam quality of booster stage induced by "defects" on optics

The “defects” on optics is the main limiting factor in enhancing the power of a high power solid-state laser system. This paper established a “defects” model about amplitude modulation based on statistics. Aimed at the booster of SG-Ⅲ prototype, the relationship between characteristic parameters of the model and the near-field quality of the beam was studied. The results show that, both the increase of total density of “defects” and the decrease of power exponent can cause the degradation of beam quality; for median-high frequency, different total densities of “defects” have approximately equal effects, while the effects of different power exponents vary; the larger “defects” can lead to more serious degradation of beam quality; for the booster, it is necessary to control the to