重力作用下大口径薄型光学元件面形的优化方法

Method for improving the additional surface of thin KDP crystal with large-aperture under gravity

高功率固体激光装置的频率转换系统中,大口径薄型KDP晶体附加面形的产生,直接影响了高功率激光的频率转换效率和光束质量.针对非垂直放置状态下的大口径平面光学元件,提出了一种用于改变并优化光学元件因重力作用产生附加面形的"杠杆式"夹持方法,并据此设计了适用于大口径超薄Ⅰ/Ⅱ类KDP晶体的夹持系统.利用ANSYS分析软件,建立了相应的有限元分析模型,仿真计算了晶体在夹持前后的附加面形变化,讨论了支撑条长度及加工误差对晶体面形优化效果的影响.研究结果表明:提出的"杠杆式"夹持方法在加工无误差时,对晶体附加面形的优化率达到了90%以上;在支撑条存在加工误差时,对晶体附加面形的优化率也达到了74%以上.

For the frequency conversion system in inertial confinement fusion （ICF）, the harmonic con- version efficiency and beam quality of high-power lasers are directly affected by the additional surface of thin KDP crystals with large-aperture. A ＂lever-type＂ clamping method for improving and optimizing the additional surface of large-aperture optical component placed non-vertically under gravity is proposed. According to this method, a specific fixture system is designed for ultra-thin type Ⅰ / ⅡKDP crystals with large-aperture. A finite element analysis model for the fixture system is established by ANSYS software. The additional surfaces of KDP crystals under gravity are simulated when KDP crystals are clamped with or without fixture system. Furthermore, the influences of the length and the fabrica- tion errors of the support bars on the optimization of the additional surface are also discussed. The results show that the additional surface variations of KDP crystals are improved above respectively 90 and 74% in the cases of without and with machining errors by the ＂lever-type＂ clamping method pro- posed in this paper.