面向KDP晶体表面缺陷钝化的微乳液射流去除机理研究

As an important optical component in high energy laser system, KDP crystal can improve its resistance to laser damage by passivating its surface defects caused by cutting. Current KDP surface treatment methods are limited by either hard-to-remove residual particles, subsurface damage, unavoidable heating effect, or surface degradation. Thus, this study proposes a novel microemulsion jet process that can be used to passivate the surface defects. This method makes use of a thermodynamically and kinetically stable microemulsion that contains nanometer range water droplets evenly dispersed in the non-aqueous carrier liquid. The sprayed out nanoscale droplets remove material through microscale dissolution without introducing new subsurface damage. This method is expected to solve the adverse effect of surface defects on the KDP resistance to laser damage. The deformation behavior of nanoscale water droplets in microemulsion will be firstly studied, and the influence of flow field on deformation rate of water droplets will be obtained. Then the mechanism of controlled removal of KDP crystal by microemulsion jet will be studied, and the removal function model will be established to reveal the mechanism of controlled selective removal of water droplet on defect high-steep transition surface. Finally, the morphology evolution of typical surface defects will be studied and the passivation law and strategy of surface defects will be obtained. The research of this project has important theoretical significance and engineering application value for KDP crystal surface treatment technology.

作为强激光装置中的重要光学元件，KDP晶体的表面缺陷钝化是提升其抗激光损伤性能的重要途径。现有的表面处理由于颗粒残留、引入亚表面损伤、热效应及表面恶化等问题限制了在表面缺陷钝化方面的进一步应用。针对现有技术的不足，本项目基于微乳液中纳米水核对KDP的可控选择性去除，提出微乳液射流钝化KDP的表面缺陷从而提升其抗激光损伤能力的思想，具有无磨料、不引入亚表面损伤、无热效应等显著优势。有望解决表面缺陷对KDP抗激光损伤性能的不利影响。研究射流状态下微乳液纳米水核与KDP相互作用过程中的变形行为，获得流场对水核变形率的影响规律；研究微乳液射流对KDP可控去除的机理，建立去除函数模型，揭示纳米水核对缺陷高陡度过渡表面实现可控选择性去除的机制；研究表面典型缺陷的形貌演变规律，探明微乳液射流对表面缺陷的钝化规律，获得KDP表面缺陷钝化策略。本项目的研究对KDP晶体表面处理具有重要理论意义和工程应用价值。

本课题将无磨料处理技术的无残留优点和射流技术的柔性、近无亚表面损伤等优点结合起来，实现了柔性、近无残留的KDP晶体超精密抛光，为改善（亚）表面质量提供了一条新的技术途径，研究表面有望可为KDP晶体亚表面缺陷的钝化提供一种技术途径。开发了低粘度微乳液作为去除介质，并分析了低粘度微乳液作为微乳液射流介质的去除特征，从可控性以及去除稳定性出发，系统研究了微乳液作为KDP晶体无磨料射流去除介质的可行性和具有的优势，获得了垂直入射抛光情况下稳定的类高斯型去除函数，解释了该去除函数的产生机理，为后续KDP晶体的表面处理奠定理论基础。采用小角掠入射X射线衍射（GIXRD）手段，建立了KDP晶体的亚表面变质层无损表征方法。基于此，探索开展了无磨料射流技术用于KDP晶体的变质层的钝化及减缓实验，结果显示该技术能够较大幅度减缓变质层厚度。为后续KDP晶体的表面处理提供一定的借鉴意义。