强光元件纳米级损伤前驱体抑制理论与方法研究

In high power laser systems, for instance, the inertial confinement fusion (ICF) device, the irradiate fluences are continuously increasing. However, the current optical fabrication method and technique, which are based on traditional sub-surface defect restraint, cannot correspondingly fulfill the demand of the systems development. The nano-scale damage precursors, such as micro-region stress on surface and micro metallic particulate matter, introduced by fabrication processes, have become the main limitation of the laser fluence rising. Except being responsible for the success of ignition of the National Ignition Facility (NIF), the problem poses a new challenge to the method and technique of high power used optical fabrication. Therefore, this project focuses on how to solve that problem and to realize further rising of laser irradiate load ability. The key is nano-scale defects researching, including the generation, the relation with damage and the restrain solution. Meanwhile, thermal-transport theory and photon-thermal absorption test are newly introduced, aiming at analyzing the production of nano-scale damage precursor and laser-induced break down mechanism, and then to construct the quantitized relationship between precursors and damage resistance ability. An innovative method for the test and characterization of nano-scale defects is also proposed. Furthermore, ion beam cleaning and polishing techniques are utilized to research the precursor restraint theory and process. Finally, this project will provide not only theories but also practical techniques to restrain the nano-scale laser damage precursors and improve the damage resistance ability of optics. In summary, efforts will be made to the further development of our domestic important high power laser systems.

在惯性约束聚变装置等强激光系统中，随着辐照通量的不断提高，抑制传统亚表面缺陷为主的光学加工理论和方法已不能满足系统发展需求，以加工带来的表面微区应力和金属微颗粒等为代表的纳米级损伤前驱体已成为制约光学系统提高使用辐照通量的主因，甚至直接关系到惯约装置能否“点火”成功，对强光光学制造理论和方法提出了新挑战。为进一步提高光学元件受强光辐照通量水平，项目系统研究光学制造过程纳米级损伤前驱体产生、作用规律和抑制方法等关键问题，引入热吸收传导理论和光热吸收检测新方法，解析纳米级损伤前驱体产生规律和诱导激光损伤机理，建立强光元件抗损伤性能和前驱体特性的量值关系，提出纳米级缺陷定量检测表征新方法，采用离子束清洁抛光技术，研究纳米级损伤前驱体抑制理论与关键工艺，为解决制约高通量使役的纳米级损伤前驱体抑制难题，提升强光元件抗激光损伤能力，提供理论依据和关键工艺，促进我国重大强激光工程的运行水平进一步提高。

研究强激光辐照下光学元件的激光诱导损伤机理及检测评价问题是一个具有理论挑战和实用价值的课题。本项目重点研究纳米级损伤前驱体诱导损伤机理、纳米级缺陷检测及其激光损伤性能表征、强光元件离子束清洁制造工艺。引入热吸收传导理论和光热吸收检测新方法，对多种损伤前驱体检测评价技术进行实验研究，建立缺陷—损伤性能—阈值之间的映射关系。利用原子力显微镜观察测量不同离子束加工深度下，微纳尺度的损伤前驱体的形貌演变，分析微纳尺度损伤前驱体的产生与演变原因。依托激光损伤阈值测试平台，获得离子束加工对材料去除不同深度与损伤阈值的关系。通过开展HF酸刻蚀和离子束加工组合工艺联合抑制缺陷的研究，表明采用先HF酸刻蚀后离子束加工的联合工艺，可将阈值提升到9.5J/cm2，并显著改善表面质量，表面粗糙度控制在1.10nmRMS。