紫外元件损伤动力学实验研究

Experimental research on the dynamics of ultraviolet laser-induced damage

对于大型强激光装置的光学系统,尤其是终端光学组件(FOA),其紫外激光损伤问题始终是制约负载能力提升的关键问题,该过程基于激光与物质相互作用及而后发生的材料效应,涉及元件材料的制备与生长、加工、环境、修复和工作参数等多种因素.为此,在长期的研究中,我们总结并定义了紫外元件损伤动力学概念和研究体系.本文着重介绍利用同步辐射及其他核技术方法开展实验研究的结果,对于熔石英元件,利用同步辐射μ-CT技术获得了损伤图像,结合同步辐射XRD确定了损伤过程和结构,解释了相应的材料效应;结合拉曼光谱,利用光热显微技术研究了损伤内部结构和发展过程,定义了激光损伤可视面积(LDAVR)的含义.利用同步辐射XRF及正电子湮灭技术对其光学加工制造影响负载能力的因素进行了物理分析;对于KDP晶体,利用同步辐射XRF-XRD的单独或联合测试,对退役元件和实验样件进行了对比研究,分析了不同运行功率下的激光损伤过程,明确了损伤坑的构成和定义,获得了损伤图像.值得指出:依据上述研究结果,针对工程上的问题,本文提出了解决或改善的方法和途径及其应用.

For a high-power laser,especially its final optics assembly(FOA),the ultraviolet(UV)laser-induced damage(LID)is always the key factor to restrict the loading capacity of the laser.The LID processes are based on the laser-matter interaction and their subsequent materials effect,involving all processes in the whole process,such as material preparation,crystal growth,processing,environment,repairing,and operation parameters.For this reason,we established the concept and research frame of the UV LID dynamics with our long-term research.This review mainly introduces our experimental results in the field used by synchrotron radiation and other nuclear techniques.For fused silica,the LID pictures were acquired by the synchrotron radiationμ-CT technique,in which the mechanism of the LID and the evolution of structures were determined by synchrotron radiation X-ray diffraction(XRD),and then explored the corresponding material effects.Combined with Raman spectroscopy and photo-thermal microscopy,the internal structure and evolution of the LID were studied,and the Laser Damage Area Vision Ratio(LDAVR)was defined.Using synchrotron radiation X-ray fluorescence(XRF)and positron annihilation spectroscopy,the factors affecting the loading capacity in optical fabrication were physically investigated.For potassium dihydrogen phosphate(KDP)crystals,the retired components and experimental samples were studied by synchrotron radiation XRF-XRD joint measurement.The LID processes under different fluences were analyzed,the structure and definition of the damaged pit were revealed,and the damage picture was explicit.Based on the above research results,it is worth pointing out that the methods and approaches to solve the problems in engineering were put forward and applied.