1064nm强激光薄膜的损伤发展特性及机理研究
文献类型：学位论文
| 作者 | 柴英杰 |
| 文献子类 | 博士 |
| 导师 | 邵建达 |
| 关键词 | 光学薄膜，结构性缺陷，坑点缺陷，激光诱导损伤，损伤阈值 Optical coatings, Structure defects, Pit defects, Laser-induced damage, Laser-resistance. |
| 其他题名 | Research of damage growth performance and mechanism on 1064nm high power laser coating |
| 英文摘要 | 目前在运行和在建的大型激光装置中，光学薄膜元件是其中的薄弱环节，其破坏问题一直是激光向高峰值功率、大能量密度方向发展的瓶颈之一。大量的针对多层膜的高功率激光损伤实验表明，在纳秒激光脉冲范围内，薄膜的损伤主要是由缺陷引起的。引发激光损伤的缺陷分为结构缺陷和吸收性缺陷两类。深入分析薄膜中缺陷的来源、缺陷的损伤特性和机理，可以针对性的优化薄膜的制备工艺、最大程度地提高抗激光损伤阈值。本文基于对强激光薄膜材料的基本物化性能、飞秒/纳秒脉冲激光技术、高阈值薄膜制备工艺、薄膜局部应力分析、薄膜与激光相互作用过程等内容的深入研究，结合大量的具有结构缺陷针对性的激光与薄膜元件相互作用实验，为高阈值1064nm激光薄膜的研制提供技术支持。具体工作如下： 针对基底-膜层耦合缺陷，从飞秒激光坑点镀制透射型薄膜后的损伤实验结果出发，结合基底亚表面再沉积层在升温过程中的出现的杂质迁移现象、采用Mie散射计算和杂质缺陷吸收模型，探究并初步定义了基底与薄膜耦合效应。在电子束热蒸发镀制的透射型薄膜中，通过采用酸洗后基底和相对低的镀膜温度，降低了耦合缺陷密度、提升该类缺陷抗强激光能力，获得了损伤阈值接近未镀膜基底表面的样品。 针对结构性缺陷，以基底（亚）表面缺陷为出发点，采用飞秒激光微加工和纳秒激光损伤相结合的方法，避免了采用机械方法加工导致的随机性亚表面裂纹对实验研究的影响，系统的研究了不同尺寸的基底人工坑点对多层膜抗损伤能力的影响。采用多种表征手段分析了坑点缺陷镀膜后的表面形貌，内部微结构和损伤微观形貌，根据薄膜生长模型建立了坑点缺陷处薄膜生长的几何关系；通过系统性激光损伤实验，分析了该类型缺陷对于薄膜损伤阈值和坑点尺寸的关系，并对损伤形貌进行了详细表征；采用有限元分析法（FEM）模拟获得了形变后膜层对缺陷处电场分布影响，并分析了由于膜层形变导致的局部应力集中；基于电场-温度场模型，通过损伤形貌和电场/应力分析结果的对应关系，解释并发展了坑点结构的热力耦合破坏模型。 针对镀膜基底（亚）表面存在的坑点/划痕缺陷，参考坑点位置薄膜生长模型，并结合精确的薄膜应力控制技术，在部分镀膜过程中采用等离子体辅助电子束沉积（PIAD）的方式，在镀制高性能激光薄膜与带缺陷的基底之间加镀一个缺陷缝合层。该方法可以有效修复由于基底凹坑缺陷导致的多层膜在横向上的变形。这种缝合基底缺陷从而平滑膜层形变的方法，可以在保证高反膜光学性质、精确控制薄膜应力和高损伤阈值的前提下，有效的抑制由于膜层形变导致的电场增强和应力集中，从而有效提高薄膜的抗激光损伤性能，是一种简单有效的高反膜损伤阈值提升技术。; In the high-power laser facilities, both being constructed and operated, optical coatings are one of the most important components and vulnerable elements. The laser-resistance on optical components is still one of bottlenecks for the development of high power laser systems. In the nanosecond region, experimental results indicated that the laser damages happened on the multilayer coatings were mostly induced by coating defects, which include structural defects and absorptive defects. By analyzing the damage source, the characteristics of damage site and damage mechanism, the laser-induced damage threshold (LIDT) could be increased by optimizing coating manufacture process. In this work, based on the physical and chemical properties of deposited material, femtosecond/nanosecond laser experiment, coating manufacture process, localized stress analyzing, laser-material interaction, combining the laser damage experiment on the coatings with artificial pitted structure embedded on the substrate, the effective solution could be proposed for the high power laser coating preparation in 1064nm. The detail of our work is listed as followings: The coupling effect between coating layers and substrate was preliminary defined. By using the Mie Theory and defect-induced absorption model, combined with the subsurface defects shifting, which was happened during the heating process of deposition, the anti-reflective coatings on the substrate pit damage was well explained. During the e-beam deposition process, the fused silica substrate was cleaned by HF acid and coated in relatively lower temperature, for the lower defects density and higher laser damage resistance. The high laser-resistance anti-reflective coatings, whose LITD were closed to the substrate, were achieved. We prepared the artificial pits by using femtosecond fabrication platform and the laser-resistance of the coated pits was tested by nanosecond laser. The femtosecond pits could effectively avoid the negative influence of the subsurface defects, which was induced by the traditional polishing process. The impacts of different sized artificial pits on the laser resistance of multilayer coatings were systematically investigated. Before and after irradiation, both the surface morphologies and the cross section of the coated pits was characterized, and the geometrical relations on of the coating layer growth model were built and analyzed. Laser resistance of different sized coated pits were tested by both 1-on-1 and raster scanning mode, and their damage morphologies were characterized. The e-field distribution of the deformational coating was calculated by Finite Elemental Method (FEM); the localized stress was investigated as well. Based on the laser induced thermal-mechanical damage model, combining with the laser damage morphologies and e-field/localized mechanical stress, the substrate pit induced damage mechanism was developed. For suturing the pits/scratches defects, the plasma-ion assisted e-beam deposition was used for fabricating the thick SiO2 layer, which could be used for restoring the lateral deformation in the functional multilayer coatings. The laser damage resistances were improved by effectively suppression the e-field enhancement and localized stress concentration, without influence the optical properties and global coating stress. |
| 学科主题 | 光学工程 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/30991]  |
| 专题 | 中国科学院上海光学精密机械研究所 |
| 作者单位 | 中国科学院上海光学精密机械研究所 |
| 推荐引用方式 GB/T 7714 | 柴英杰. 1064nm强激光薄膜的损伤发展特性及机理研究[D]. |
入库方式： OAI收割
来源：上海光学精密机械研究所
浏览0
下载0
收藏0
其他版本
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。