KDP/DKDP晶体元件新型功能化学膜研究

In ICF research, high laser damage threshold, high stability and good moisture-proof properties for the chemical coatings of the KDP/DKDP crystal frequency conversion elements are highly demanded for the high power laser systems. However, the crystal transition temperature of DKDP is relatively low, and it is quite sensitive to the moisture, these properties are considerably limiting the preparation and processing technology of the coatings, thus the properties of the coatings are quite limited, and they would not match the increasing demands for the future devices. To solve this problem, this research project firstly focuses on the fundamental research of the sol properties and the coating structures, then investigates sol synthesizing, micro-structure controlling, and the relationship between their micro and macro properties with the final functions of the coatings. Main emphasizes are put on the low temperature coating synthesizing mechanism, preparation and processing technologies; the properties and evolution rules of the coatings changing with the intense laser irradiation as well as the contamination of the special vacuum conditions; developing the coatings’ laser damage threshold and their abilities of the contamination resistance; realizing the new technology for the complex functional sol-gel coatings of KDP/DKDP crystal elements; providing the basic theory and the practical key technology for the preparation and application of the new multi-functional chemical coatings for the KDP/DKDP crystal frequency conversion elements for the future large laser facilities of our country.

在ICF研究中，高功率激光装置要求频率转换KDP/DKDP晶体元件的溶胶-凝胶膜具有高激光损伤阈值、对环境稳定、防潮性能好且能量传输效率高的复合功能和特性。但由于DKDP晶体元件晶相转变温度低、对湿度特别敏感，在很大程度上限制了膜层制备和后处理工艺，从而对膜层性能产生较大的负面影响，无法满足未来装置的使用要求。本项目针对该现状，从溶胶特性和膜层结构的基础性研究入手，探索溶胶合成、微结构控制，及其微观、宏观特性与膜层最终性能之间的规律性关系。重点研究膜层的低温合成机理、制备和后处理工艺；膜层在强激光辐照及复合真空污染的特殊工作环境条件下的特性和演变规律，提高其强激光耐受性和抗污染能力，实现KDP/DKDP晶体溶胶-凝胶薄膜新型复合功能的工艺途径，为我国未来大型激光装置的KDP/DKDP晶体元件的新型化学膜制备工艺研究与应用提供必要的基础依据和实用或可借鉴的关键技术。

KDP/DKDP晶体是高功率激光系统中必不可少的三倍频激光转换光学元件，但由于其在空气中极易潮解发雾，使用过程中通常需要镀制防潮保护膜。本项目着重研究了SiO2溶胶的改性处理，通过添加不同修饰剂，钝化SiO2颗粒，降低表面能，进而得到具有高激光损伤阈值及优良防潮性能的溶胶-凝胶光学减反膜。通过辛基三甲氧基硅烷对溶胶的修饰，获得了具有耐潮湿环境稳定性的薄膜，在相对湿度90%RH环境中放置4周后透过率仅下降0.23%。探究回流前、回流后添加修饰剂六甲基二硅氮烷（HMDS）对溶胶pH值的影响，结合KDP/DKDP晶体弱酸性的特点，最终确定采用回流前添加修饰剂的方式制备改性溶胶。由HMDS改性溶胶制备的薄膜具有良好的疏水性能，水接触角为156°，且在55%RH环境中放置4个月透过率仅下降约0.3%，真空环境污染1个月下降约0.5%。镀膜后的KDP晶体元件在351nm处透过率达99.3%，激光损伤阈值为11.40J/cm2（355nm, 3ns）。本项目的研究成果为KDP/DKDP晶体原件的防潮减反膜的制备与应用提供了必要的科学依据和技术参考。KDP/DKDP晶体是高功率激光系统中必不可少的三倍频激光转换光学元件，但由于其在空气中极易潮解发雾，使用过程中通常需要镀制防潮保护膜。本项目着重研究了SiO2溶胶的改性处理，通过添加不同修饰剂，钝化SiO2颗粒，降低表面能，进而得到具有高激光损伤阈值及优良防潮性能的溶胶-凝胶光学减反膜。通过辛基三甲氧基硅烷对溶胶的修饰，获得了具有耐潮湿环境稳定性的薄膜，在相对湿度90%RH环境中放置4周后透过率仅下降0.23%。探究回流前、回流后添加修饰剂六甲基二硅氮烷（HMDS）对溶胶pH值的影响，结合KDP/DKDP晶体弱酸性的特点，最终确定采用回流前添加修饰剂的方式制备改性溶胶。由HMDS改性溶胶制备的薄膜具有良好的疏水性能，水接触角为156°，且在55%RH环境中放置4个月透过率仅下降约0.3%，真空环境污染1个月下降约0.5%。镀膜后的KDP晶体元件在351nm处透过率达99.3%，激光损伤阈值为11.40J/cm2（355nm, 3ns）。本项目的研究成果为KDP/DKDP晶体原件的防潮减反膜的制备与应用提供了必要的科学依据和技术参考。