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题名	飞秒激光诱导下色散补偿元件的损伤机理研究
作者	邢昕
文献子类	硕士
导师	冷雨欣
关键词	飞秒激光泵浦探测 femtosecond laser pump-probe technique 超快激光损伤动力学 ultrafast laser damage dynamics 啁啾镜 chirped mirror 多层介质光栅 multilayer dielectric grating
其他题名	Carrier dynamics in dispersion compensation element induced by femtosecond laser
英文摘要	飞秒激光具有极为优良的时间和空间分辨特性、超高的光谱带宽以及极高的峰值功率，得到了广泛的研究与应用。其中，光学薄膜元件，特别是以介质膜为主要组成部分的色散补偿元件，是飞秒激光系统的关键组成部分之一，对飞秒激光系统性能的提升具有重要意义。然而，薄膜的损伤阈值一直是限制飞秒激光发展的主要原因之一，因此，研究飞秒激光诱导下色散补偿元件的损伤机理，探寻提升色散补偿元件的损伤能力具有重要科学意义和应用价值。 本论文基于中心波长800nm、重复频率1kHz的Ti: sapphire飞秒激光系统，通过泵浦探测技术，针对超快激光系统中色散补偿元件，进行飞秒激光作用下介质膜的损伤动力学研究。基于波尔兹曼传输方程，对介质膜内部载流子运动过程进行分析，进一步深入了解了飞秒激光作用下色散补偿元件的损伤过程。取得了如下研究成果： 1. 基于泵浦探测技术，发展了飞秒激光损伤测试技术，在保证测量高精度的同时，能够对飞秒激光辐照下的介质膜进行实时无损探测。应用超高分辨的测试装置，得到了介质膜材料的归一化反射率随时间及波长的演变图像。 2. 利用飞秒激光泵浦探测实验，对Nb2O5/SiO2啁啾镜表面介质膜这一复杂混合膜系的飞秒激光损伤超快动力学进行研究。基于光致电离、碰撞电离、以及其他非线性作用过程对损伤行为进行分析，得出了实验中探测光反射率下降的主要原因是介电材料内的载流子吸收的结论。完善了由Keldysh光致电离模型，Drude碰撞电离模型，和跃迁过程中的电子衰减过程共同组成的理论模型，得到了该膜系损伤阈值与缺陷态电子吸收截面的依赖关系。 3. 利用泵浦探测技术，对多层介质光栅的表面高反射率膜层在飞秒激光辐照下的超快动力学进行了研究。观察到具有时间分辨特性的材料反射率变化情况，得出了反射率下降主要是激光诱导产生的导带电子的吸收导致的结论。在759nm和785nm两个不同的波长，存在两个不同的吸收峰，对应于不同的弛豫时间。发现并解释了飞秒激光作用下，最初发生多光子电离的Ta2O5层并不是最先受到破坏的部分这一现象。; Femtosecond laser has been widely studied and applied due to its excellent temporal and special resolution, wide spectral bandwidth and high peak power. Optical thin film components, especially for the dispersion compensation components, is one of the critical components to improve the femtosecond laser system. However, the damage of compensation components film always limits the development of femtosecond laser. Therefore, it is of great significance to study the damage mechanism of the dispersion compensation element under femtosecond laser and to explore the possible method to enhance the damage resistant ability of the dispersion compensation element based on it. In this paper, the femtosecond pre-breakdown dynamics of dielectric films in ultrafast laser system is investigate by femtosecond pump-probe spectroscopy based on the Ti: sapphire femtosecond laser system with the center wavelength of 800 nm and the repetition frequency of 1 kHz. And then the carriers transition process in dielectric films is analyzed by Boltzmann transport equations, which is helpful for understanding the femtosecond laser induced damage process in the dispersion compensation elements. This study achieves results as follows: 1. Based on the pump-probe technique, the femtosecond laser damage testing device is modified, which provide an accurate method to detect the ultrafast laser damage process in multilayer dielectric films. The time-resolved reflectivity change as a function of wavelength in dielectric film materials are obtained and provide experimental basis for ultrafast dynamics research inside the material. 2. The femtosecond laser induced ultrafast carrier dynamics related to damage in multilayer dielectric films of Nb2O5/SiO2 chirped mirror, which is a complex and hybrid film, is investigated by pump-probe spectroscopy. Based on the analysis of the damage behavior in the process of photoionization, impact ionization, and other nonlinear processes, it is concluded that the main reason for the probe laser reflectivity decline is the carrier absorption in the dielectric material. A theoretical model with Keldysh photoionization model, the Drude impact ionization model, and the electron decay process in the transition process was improved. And the dependence of the damage threshold of the film and the electron absorption cross section in defect state is obtained. 3. The ultrafast dynamics of high reflectivity coatings in multilayer dielectric gratings under femtosecond laser irradiation is studied using the pump-probe technique. The variation of the reflectivity of the material with fs time resolution is observed, which is mainly caused by the absorption of the conduction band electrons induced by the laser. There are two different absorption peaks corresponding to different relaxation times at 759 nm and 785 nm, respectively. It is found that the Ta2O5 layer, which is ionized by multiphoton ionization initially, is not the first to be destroyed.
学科主题	光学工程
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/31017]
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	邢昕. 飞秒激光诱导下色散补偿元件的损伤机理研究[D].

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