QQ客服 官方微博 反馈留言

题名	石英元件损伤修复技术研究
作者	周丽
学位类别	硕士
答辩日期	2016
授予单位	中国科学院上海光学精密机械研究所
导师	李学春
关键词	石英元件 损伤修复 CO2激光 修复形貌 激光诱致损伤阈值
其他题名	Research on Mitigation Technology of Laser Induced Damage on the Fused Silica Optics
中文摘要	光学元件的激光诱致损伤及其增长是限制高功率激光驱动器最高运行通量密度的主要因素，其中三倍频石英元件的负载受限问题尤其严重。基于提升石英元件的抗损伤能力，本文开展CO2激光修复技术研究，旨在探求最佳的修复形貌以及修复工艺，有效抑制元件发生损伤及其增长，提高石英元件的利用率，缩减高功率激光驱动器的运行成本。文章主要内容如下： 1）建立FDTD模型模拟计算不同修复形貌下石英元件内部修复区域的光强分布，并分析修复坑侧壁与法线的夹角对元件修复区域的光强极大值及其所在位置的影响?结果表明，当夹角大于70°时元件修复区域光强极大值小于1.66，才能够有效抑制石英元件的损伤及其增长；并且，在夹角大于42°范围内，随着夹角的增大，元件修复区域内光强极大值逐渐减小? 2）在元件修复区域模拟结果的基础上，进一步建立衍射传输模型模拟计算不同形貌修复坑对其后续光场的调制。结果表明，侧壁与法线夹角为70°、宽200μm的抛物面型、圆锥型和圆台型凹坑的后续光强极大值小于1.46，通常不会对高功率激光驱动器中的后续光学元件产生破坏?但是，当修复坑宽度较大（1mm）时，圆台型凹坑的后续光强极大值高达9.31，极易对后续光学元件产生破坏?因此，考虑目前实际激光加工水平，侧壁与法线夹角大于70°的圆锥坑是石英元件后表面的最佳修复形貌。 3）在线性扩散近似下，即假设热导率等参数不随温度变化并且忽略辐射和表面热耗散的影响，建立热力学模型计算激光修复过程中不同脉宽和不同焦斑大小下石英表面温度场，从而获得激光脉冲烧蚀熔石英材料的能量密度阈值。并进一步对CO2激光脉宽、脉冲能量、焦斑大小以及光斑扫描路径等影响修复形貌的关键因素进行分析实现了修复形貌的优化，得到满足形貌要求的修复坑。 4）在综合各要素分析的基础上，制定并演示了基本修复工艺，开展了相关验证实验，完成了单脉冲修复工艺研究。处理样件的测试结果表明，在脉冲能量密度达到阈值条件时，单脉冲修复坑的三倍频损伤阈值均高于10J/cm2，且CO2激光脉宽越短，损伤阈值越高，最高达14J/cm2。
英文摘要	Initiation and growth of laser induced damage in optics is a major factor limiting the maximum operating fluence of high power laser driver, among which the problem of load restrained is especially severe for 3 omega fused silica optics. Based on improving the damage resistance performance of fused silica optics，the mitigation technique using CO2 laser is researched in this thesis, aimed to find out the optimum mitigated morphology and mitigating process, which can effectively inhibit the initiation and growth of laser induced damage to increase the utilization rate of fused silica optics and reduce the operation cost of high power laser driver. This thesis consists of 5 sections as follows: 1) The FDTD model is established to simulate and calculate the local intensity distributions in the fused silica optics with different mitigated morphologies, and the influence of the angle between the wall of the mitigated pit and the surface normal of optics on the maximum intensity and its location in the mitigated area on the optics is analyzed. The results show that when the angle is over 70 °, the maximum intensity inside the mitigated optics is less than 1.66, then the initiation and growth of laser induced damage are effectively inhibited. In addition, within the angle range lager than 42°, the maximum intensity inside the mitigated optics decreases gradually with the angle increasing. 2) Based on the conclusions above, the diffraction propagation model is established further to simulate and calculate the modulations of the subsequent intensity with different shape repair pits in a certain distance range (0.1~2m). The calculations show the maximum subsequent intensities of a pit in shape of parabolic surface, cone and truncated cone are all less than 1.46 with an angle of 70° and width of 200μm, which is not easy to induce damage on the downstream optics. But when the width of pit increases, to 1mm, for instance, the maximum subsequent intensity is as high as 9.31, which would damage the downstream optics easily. Thus, given to the difficulty of laser machining technology, a conical pit with an angle larger than 70° is the first choice for the damage mitigation on the rear surface of fused silica optics. 3) Using the diffusive linear approximation, i.e., assuming that the thermal properties are constant over the temperature range of interest and neglecting radiative and surface heat loss, the thermodynamic model is built to calculate the temperature field on the surface of fused silica under different pulse widths and different spot sizes in the process of laser mitigation, and find pulse fluence threshold of laser well ablating the fused silica. Further, key factors that affect the mitigated morphology such as pulse width, pulse energy and focal spot size of CO2 laser and the spot scan path are studied to optimize the mitigated morphology and obtain the pit meeting the requirements. 4) Under the analysis of key factors, the basic mitigated process is developed and demonstrated, and the relevant verification experiments are implemented, that is, the study of the single pulse mitigated technique is realized. The test results of the processed samples indicate that once the pulse fluence reaches the threshold, the damage thresholds of the mitigation pits fabricated by single pulse are all higher than 10J/cm2, and the shorter the pulse width, the higher the damage threshold, up to the highest of 14J/cm2.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/16987]
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	周丽. 石英元件损伤修复技术研究[D]. 中国科学院上海光学精密机械研究所. 2016.

个性服务

查看访问统计

相关权益政策

暂无数据

收藏/分享

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。