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题名	YAG晶体上薄膜的力学和激光损伤性能研究
作者	王河
学位类别	博士
答辩日期	2013
授予单位	中国科学院上海光学精密机械研究所
导师	贺洪波，张伟丽
关键词	光学薄膜，YAG 晶体，力学性能，激光损伤性能，低温条件
其他题名	Mechanical properties and laser-induced damage behaviors of optical coatings on YAG crystals
中文摘要	全固态激光器以其高效率、长寿命等优势成为新一代的优质光源，而随着全 固态激光器小型化、集成化的发展趋势，要求直接在晶体上镀制光学薄膜。由于 晶体的物理性质如热膨胀系数、热导率等的各向异性和表面的特殊性，其上薄膜 的力学性能与其他基底材料如K9 等并不一样；同时，光学薄膜的抗激光损伤特 性将直接影响整个全固态激光器系统的设计及运行性能，研究薄膜的激光损伤问 题非常重要；并且由于Yb: YAG 激光器经常应用在航天空间低温环境中，低温 对薄膜的光谱性能和损伤性能的影响不容忽视。据此，本文研究了YAG 晶体上 薄膜的力学和激光损伤性能，以及低温环境中薄膜的激光损伤性能。 采用纳米划痕仪表征了晶体基底和玻璃基底上薄膜的力学性能，分析了薄膜 微结构、弹性模量对其附着性能的影响，结果表明薄膜在YAG 晶体基底上的粘 附失效临界载荷小于在K9 基底上。分析认为：薄膜与K9 玻璃基底机械结合比 较牢固，与YAG 晶体基底由于晶格不匹配而导致膜基界面处的残余应力较大， 增加了膜基剥离应力；同时，薄膜与YAG 晶体的弹性模量不匹配度较K9 玻璃 基底更大，由此导致YAG 晶体上薄膜的粘附失效临界载荷较小。 利用根据国际标准ISO11254 建立的薄膜损伤测试系统获得了YAG 激光系 统中常用薄膜（减反射膜、高反射膜和波长分离膜）的激光损伤性能。结果表明 在YAG 基底上的薄膜损伤阈值低于在K9 基底上。利用界面吸收理论、一维鼓 包模型和热力破坏机制从缺陷诱导过程和热力破坏过程两方面说明了薄膜阈值 降低的原因。发现减反射膜从K9 基底上剥离所需的温升是YAG 的4 倍以上， 以量化数据客观的证实了薄膜的附着性能对其激光损伤性能的影响。 研究了退火对减反膜、高反射膜的抗激光损伤性能影响。研究表明退火对镀 制在YAG 晶体基底上的薄膜性能影响较小，对K9 基底上的薄膜性能影响较大。 两种基底上呈多孔状结构的薄膜具有不同的致密度，导致退火过程对其抗激光损 伤性能的影响不一样。 采用低温冷却装置研究了低温真空环境中高反射膜和减反射膜的激光损伤 性能。结果表明对于大气环境，薄膜在低温真空环境下的激光损伤阈值降低。分 析和讨论了低温真空环境下的独特破坏现象产生的原因：1.低温真空环境导致膜 层的热导率降低，在同样的激光能流辐照下膜层的温升增大，抗激光损伤能力降 低；2.再沉积层由于热应力的作用使亚表面层的致密结构遭到破坏，溢出基底表 面的颗粒在基底的表面或亚表面区形成新的缺陷，造成基底与减反射膜体系的整 体破坏。 薄膜的力学性能、抗激光损伤性能与薄膜的微观结构三者之间密切相关，了 解研究各个因素之间的关系，对于促进激光薄膜材料学的发展和完善、研制性能 优良的光学薄膜具有重要的学术意义。
英文摘要	The diode pumped laser(DPL) is a high-quality light source with high efficiency and long life. With the development of miniaturization, compactness of DPL, optical coatings are intended to deposit on the optical crystals directly. Due to the special physical properties of the crystal such as thermal expansion coefficient and thermal conductivity anisotropy, the films on the crystal substrates show unique mechanical properties; Meanwhile, the resistances to the laser irradiation of the optical films have impacts on the performances of the whole DPL system, and the laser-induced damage behavior of the optical film is an very important issue; Yb:YAG lasers are often used under cryogenic condition, the impact of low temperature on the performance of the film cannot be ignored. According to this, mechanical properties and laser-induced damage behaviors of the films on the YAG crystal were studied in this thesis, and also the laser-induced damage behaviors at cryogenic condition were explored. First of all, the mechanical properties of films on crystal and glass substrates were obtained with nano-scratch tests, and the influences of the microstructure and elastic modulus on the adhesive properties were analyzed. The results showed that the critical loads of films on YAG crystal were lower than that on the K9 glass sustrate. The binding state between film/substrate and the modulus mismatch were taken to explain the different properties of films on two substrates: the larger residual stress at the interface of film and YAG crystal increased the peeling stress. At the same time, the modulus mismatchs between the films and YAG crystals were larger, which led to the lower critical loads of the films on YAG crystals, comparing to the K9 substrates. Then, the laser-induced damage behaviors of films using in YAG laser system such as anti-reflective coating, high-reflective coating and beam splitters were studied. The experimental setup of the laser-induced damage procedure was based on international standard ISO11254. It was found that the laser-induced damage threshold(LIDT) of coatings on YAG were lower than that on K9. Based on the thermal-mechanical damage and defect-dominated damage mechanisms, interface absorption theory, one-dimensional blister model was adopted to explain the damage behaviors of the films on the YAG crystals. It was found that the temperature-rise which could peel off the anti-reflective film from the YAG crystal was more than 4 times compared to the K9. Quantitative results were given and the relationship between the mechanical properties and the laser-induced damage behaviors was confirmed. Moreover, the impacts of post treatment methods on the damage characteristics of anti-reflective coatings and high-reflective coatings were discussed. It was found that the post treatment method has different effects on the laser induced damage behaviors of film on YAG and K9 substrates. The different packing densities of the films on YAG and K9 are probably the reason of the difference. Finally, the damage characteristics of anti-reflective coatings and high-reflective coatings under cryogenic-and-vaccum condition were investigated. The results showed that compared to normal atmospheric conditions, optical thin films have a decreasing LIDTs under cryogenic-and-vaccum conditon. Reasons of the unique damage behaviors were analyzed and discussed. 1. The thermal conductivity of the film decreased under cryogenic-vacuum condition, which could lower the LIDTs. That means, when irradiated under the same laser energy, the temperature of the film was larger than that under normal atmospheric conditions. 2. When the temperature was much lower than room temperature, the embedding particles could be spurted out from the re-deposition layer of the polished substrate due to thermal stress. These particles could precipitate to the surface of the substrate and existed as new absorptive defects, which are responsible for the initial of film damages. The mechanical properties, laser-induced damage behaviors and the microstructure of the film are colsely related. Understanding the relationship among them has an important academic significance for the development and promotion of thin-film materials science.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15745]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	王河. YAG晶体上薄膜的力学和激光损伤性能研究[D]. 中国科学院上海光学精密机械研究所. 2013.

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