KDP功能晶体表面微缺陷的修复机制及其对抗强激光损伤能力的影响研究

The optical transmission properties and service life of functional KDP crystal have been badly limited by the laser induced surface micro-defects. Aiming at the issues of mechanism for repairing these micro-defects and its influence on laser-induced damage resistance, this work will be carried out following four aspects. The influence law of the micro-defects characteristic parameters (e.g., morphology, diameter size, and defect depth) on high power laser induced damage is to be intensively studied. Meanwhile, the removal mechanism of defective material will be theoretically analyzed and the critical conditions of brittle-ductile transition for the acquirement of repaired super-smooth surface during repair process by precision micro-milling are also to be obtained. Moreover, the influence regulations of geometric parameters of diamond ball end mill and cutting parameters on the formation of super-smooth surface would be discussed and the effect of mechanical properties such as crystalline anisotropy on the repair quality would be also explored. In addition, the mapping relationship between the repaired topography characteristics and laser-induced damage threshold of KDP crystal will be investigated and the predicted life curve of repaired KDP crystal will be achieved after comprehensive evaluation of the optical properties and the resistance against high power laser induced damage. This work may not only provide theoretical basis for improving both the laser transmission properties and service life of functional crystal components, but also offer parameter references for effective repairing of full scale crystal elements in engineering application. Therefore, making an in-depth study of this project has profound scientific significance and practical values.

KDP功能晶体表面的激光损伤微缺陷严重限制了自身的光学传输特性及其使用寿命，课题针对该晶体表面微缺陷的修复机制及其对抗激光损伤能力的影响问题，深入研究晶体表面微缺陷的形状特征、直径尺寸、缺陷深度等参数对其激光损伤的影响规律；理论揭示微缺陷微铣削修复过程中材料的去除机理，获取可实现微缺陷表面超光滑修复的脆塑转变临界条件；探索材料各向异性等机械特性对微缺陷修复质量的影响程度大小，研究微修复时金刚石球刀几何参数、切削工艺等对超光滑表面形成的影响规律；探讨晶体修复后其表面形貌特征与激光损伤阈值的映射机制，对微缺陷修复后晶体的光学性能与抗损伤能力等进行综合评价，给出其修复后晶体表面对抗强激光损伤能力的寿命预测曲线。课题的研究可为提升功能晶体元件的激光传输特性及其使用寿命提供理论基础，并为大口径晶体元件在工程应用过程中的有效修复提供参数依据。因此，对本课题进行深入研究有着重要的科学意义与实用价值。

KDP晶体表面激光损伤微缺陷严重影响了自身光传输性能和使用寿命，从而大大限制了其在激光核聚变工程中应用。针对晶体表面微缺陷的修复机制及其对抗激光损伤能力的影响问题，开展了微缺陷形貌特征参数对激光损伤的影响规律、缺陷点精密微铣削修复时材料去除机理、修复时超光滑表面形成机制、缺陷修复对元件抗激光损伤能力影响等方面研究工作。主要研究成果如下：.1、建立了KDP晶体表面微缺陷诱导激光损伤的理论模型，解析了微缺陷特征参数对激光传输性能的影响规律，获得了微缺陷与激光损伤阈值间映射关系；研究确定了脆性破裂点是降低抗激光损伤能力的主要因素，获得了多脉冲激光辐照下晶体表面损伤点的增长趋势，并揭示了其急剧扩展的内在物理机制。.2、采用球头微铣刀实现了晶体表面缺陷点的精密修复，建立了缺陷表面与修复表面对激光传输性能影响的仿真模型，理论研究了修复点结构参数对晶体内部光强增强的影响规律；通过理论分析与实验研究，获得了晶体材料微铣削修复时的脆塑转变临界条件。该研究为全口径晶体表面缺陷点的塑性域修复及最优修复策略的制定提供了参数指导与理论依据。.3、通过对现有机床升级改造，搭建了晶体表面缺陷点的微铣削修复装置；实验研究了晶体材料各向异性、球头微铣刀几何参数、工艺参数等对修复表面质量的影响规律，获得了最优的缺陷点微修复参数，加工出超光滑的修复表面。该研究为大口径晶体元件微铣削修复时刀具选择及工艺参数制定提供了重要理论基础。.4、综合对比了表面微缺陷修复前后形貌特征对激光传输性能的影响，揭示了缺陷点微铣削修复机理；对修复后晶体元件实施了激光能量负载考核，并系统研究了微铣削修复刀痕和残留高度对修复质量的影响程度大小。该研究为修复后晶体元件表面完整性评价提供了重要数据支撑。.项目发表学术论文20篇，其中SCI收录14篇，IF因子总计28.728，单篇最高IF因子5.228；获省部级奖1项；授权发明专利9项，受理4项；培养青年教师2人，博士生3人，硕士生7人。