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摘要光学薄膜元件是激光器及相关光学系统中的重要元件之一，其抗激光损伤能力不足往往限制着高能量和高功率激光器的发展和应用。国内外众多科研工作者对激光致光学薄膜的损伤问题进行了大量的实验探究，将损伤机制主要归结为雪崩电离、多光子吸收、杂质诱导吸收和热应力损伤等机制。 本文建立了膜-基系统的物理分析模型， 基于温度场理论和有限元方法计算了ns 和 ms 脉宽激光对辐照光学薄膜元件的温度场分布，分析了不同脉宽激光辐照下的径向、轴向温度场分布规律及最高温度值随时间的变化。在单脉冲及重复频率脉冲情况下，完成了 10ns与1ms 激光辐照光学薄膜元件温度场的有限元模拟，并分析了重复频率对 ns 与 ms 激光损伤过程影响差异。研究结果可为激光器设计时对光学薄膜元件的要求及激光刻蚀薄膜应用中对激光参数的选择提供参考。60435
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毕业论文关键词: 重复频率；光学薄膜；激光损伤；温度场
Title The Difference of Repetition Frequency on Temperature Field of Optical Coatings Induced by Millisecond and Nanosecond Lasers
Abstract The thin optical coating is one of important lasers and associated optical systems, the resistance to laser damage of which limits the development and applications of high energy and high power lasers. Many theoretical and experimental studies have been conducted by researchers over the world, the damage mechanisms are summarized as avalanche ionization, multiphoton absorption,defects absorption and thermal stress damage. A film-substrate physical model is build to calculate the temperature field of optical coatings induced by millisecond and nanosecond lasers based on temperature theory and infinite element method. Distribution of transverse and longitudinal temperature field enduced by various pulsewidths,as well as their changing highest temperatures over time are analyzed. The infinite element simulation of temperature field of optical coatings induced by ms and ns lasers are conducted under single-pulse and repetition frequency.The difference of damage enduced by ms and ns lasers under repetition frequency is analysed. The results could provide reference for the requirements of the optical coatings when designing the optical component and for selecting the laser parameters in the film laser etching.
Keywords the repetition frequency optical film laser-induced damage temperature field
目次
1引言.1
1.1研究背景及意义.1
1.2国内外研究现状.1
1.3本文主要研究内容..5
2光学薄膜的激光损伤特性研究6
2.1光学薄膜的激光损伤机理..6
2.2激光与光学薄膜相互作用的热效应9
2.3激光与光学薄膜相互作用的场效应..11
3激光辐照光学薄膜的温升效应研究..13
3.1有限元理论简介.13
3.2激光辐照光学薄膜温度场的有限元分析..14
3.3膜-基系统的物理模型..15
4ns和ms激光作用于光学薄膜的温度场有限元模拟16
4.1单脉冲下Si02单层膜温度场计算..16
4.2重复频率对ms脉宽激光辐照薄膜元件的热效应影响..20
4.3重复频率对ns脉宽激光辐照薄膜元件的热效应影响..22
4.4重复频率对ms和ns激光脉宽辐照薄膜元件的热效应差别.25