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题名	355nm高功率激光薄膜的研制
作者	刘光辉
学位类别	博士
答辩日期	2011
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
关键词	355 nm，激光损伤阈值，高反膜，增透膜，界面层
其他题名	Preparation of optical coatings for 355 nm high power laser system
中文摘要	随着激光系统工作波长向紫外延伸，到了355 nm甚至更低(248 nm, 193 nm)的紫外波段，常用的光学薄膜材料本征吸收增大，使得薄膜在紫外高功率激光作用下更容易被破坏。本文以提高紫外高功率激光薄膜损伤阈值为目标，探索适合应用于紫外-355 nm的激光薄膜材料体系，重点探讨355 nm高反膜和增透膜的阈值提高方法，并对其破坏过程和机理进行分析。具体工作如下： 选取在355 nm具有应用潜力的Sc2O3, LaF3, MgF2, Al2O3等宽带隙薄膜材料，优化其单层膜的制备工艺，探索其最佳制备工艺参数。分别讨论了沉积温度，氧分压，蒸发速率等条件对薄膜性能的影响，为制备355 nm高功率激光薄膜(高反膜和增透膜)打下基础。 采用LaF3 /MgF2研制了355 nm增透膜，讨论了基底温度对样品激光损伤阈值的影响；利用HF酸刻蚀技术去除基底亚表面缺陷，大幅度提高了增透膜的激光损伤阈值。 研制了Sc2O3 /SiO2 高反膜，获得了5-8 J/cm2的激光损伤阈值，在氧化物高反膜体系中属于比较高的水平。为了获得更高的激光损伤阈值，又制备了不同周期数的355 nm LaF3 /MgF2 高反膜，其中(LaF3 /MgF2)16膜系获得了平均21.3 J/cm2以上的高激光损伤阈值。但是随着膜层数继续增大，LaF3 /MgF2 高反膜由于应力过大而出现了裂纹，严重影响了其抗激光损伤能力，一定程度上限制了该材料体系在355 nm高反膜中的应用。 为了避免因应力而导致的膜裂现象的发生，同时充分挖掘氟化物薄膜材料在紫外高功率激光薄膜中的应用潜质，我们采取了两种方案：一是将MgF2与Al2O3组合制备355 nm高反膜，二是采用HfO2 /SiO2 /LaF3 /MgF2膜堆制备组合高反膜，在获得了99 %以上反射率的同时，即解决了膜裂问题又稳定获得了6-10J /cm2的激光损伤阈值。 理论上，借助温度场理论模型分析了界面吸收层对不同周期数的LaF3/MgF2 高反膜的影响，分析了其激光损伤过程和特点，并结合实验结果，证明了界面吸收层是高功率激光作用下薄膜破坏的源头之一。
英文摘要	As the working wavelength of laser system extends to UV region, for example to 355 nm and even shorter (248 nm and 193 nm), intial absorption of the common opticlal materials gets extremely large, which make the damage much more easily happen when UV laser interact with the optical thin films. The main purpose of this work is to improve the laser induced damage threshold (LIDT) of the UV films for high power laser systems, and to explore film materials those are suitable to be used in 355 nm laser system, to find methods improving the LIDT of 355 nm high reflectors (HR) and anti-reflectors(AR) coatings, the damage process and mechanism will be discussed, too. The detailed work is as followings: Selecting wide band gap materials such as Sc2O3, LaF3, MgF2, Al2O3 as potential film materials, optimized the deposition process of single layers individually to get the optimized deposition parameters. The effects of deposition temperature, oxygen partial pressure and deposition rates on the properties of the films were discussed, which were the basis of preparation of coatings for 355 nm coatings. 355 nm-AR films of LaF3 /MgF2 were prepared, and substrate temperature effects on the LIDT of the samples were discussed. The new etching method which eliminated the sub-surface defects of the substrate, with HF acid as its solvent, helped us get a huge improvement (about 100% and above) of LIDT of the AR films. Sc2O3 /SiO2 high reflectors were prepared and the LIDTs of 5-8 J/cm2 of the high reflectors were gotten, which served as superior ones in oxide high reflectors. Various layer-pair number of 355nm high reflectors of LaF3 /MgF2 were prepared and the average LIDT of high reflectors (LaF3 /MgF2)16 was as high as 21.3 J/cm2. But, as the layer-pair number continued to increase, the high reflectors cracked because of huge tensile stress in the inner of the coatings, which was fatal to the laser resistance of the reflectors and limited their application in 355 nm high power laser system seriously. With the purpose of avoiding the coating cracking, as well as developing the application potentials of fluoride films in 355 nm high power laser system, two schedules were adapted: one was using Al2O3 and MgF2, to prepare 355 nm high reflectors, the other was to prepare double stacked high reflectors of HfO2 /SiO2 /LaF3/MgF2. The reflectance as high as 99 % and LIDT of 6-10 J /cm2 was gotted without coating cracking happened. When it was for the damge process and mechanism, the interfacial absorbing layer (films and substrate) was introduced, with the help of temperature field model, to analyze the effects of the absorbing interfacial layer on the LIDT results and damge process(morphology, crater depth) of LaF3/MgF2 high reflectors with various layer-pair number, and the absorbing interfacial layer was proven to be one of the important sources of damage during the high power laser and films interaction process.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15669]
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	刘光辉. 355nm高功率激光薄膜的研制[D]. 中国科学院上海光学精密机械研究所. 2011.

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