瞬态缺陷诱导激光损伤的物理过程及机理研究

Steady and transient defects can decrease the laser damage threshold of optical component by two orders of magnitude. A lot of work has been devoted to study the correlation between laser damage resistance and steady defects, but rarely reported the transient defects, which were induced by high power laser irradiation. During the irradiation of nanosecond high power laser, transient defects are already formed after several picoseconds, so in the trailing edge of the pulse, they will become a key factor inducing laser damage. This project aims to study on the key technologies, physical processes and basic principles of laser damage induced by transient defects. A challenging technical problem of ultrafast detection of transient defects during the process of laser irradiation will be solved by a pump-probe method combining stretching and amplification technology. The influence of all types of transient defects on laser damage thresholds will be studied, and the relationship among transient defects, steady defects and intrinsic material will be analyzed to reveal the changes of material properties during laser damage formation. Then the physical process of single-shot laser damage induced by transient defects will be determined. Furthermore, the relaxation characteristics of transient defects will be analyzed to study multiple-shot accumulated damage. The implementation of this project will make up for the deficiency in our current knowledge of the changes of material properties during the formation of laser damage, and promote the development of improving laser damage threshold.

稳态和瞬态缺陷使得光学元件抗激光损伤性能降低了两个量级。目前大量研究工作阐述各类稳态缺陷与激光损伤的关系，但是对于强激光诱导的具有一定弛豫时间的瞬态缺陷却少有报道。纳秒强激光辐照下经过数皮秒时间瞬态缺陷就已经形成，于是在脉冲后沿它将成为诱导损伤的关键因素。本项目以研究瞬态缺陷诱导激光损伤所涉及的关键技术、物理过程、基本原理等基础科学问题为目标，采用泵浦-探测手段结合展宽、放大技术解决强激光辐照过程中瞬态缺陷超快探测等关键技术，深入开展瞬态缺陷与本征材料、稳态缺陷之间的关联研究，阐明材料特性变化规律，结合各类瞬态缺陷对损伤阈值的影响规律确定其诱导单脉冲激光损伤的物理过程，并探讨瞬态缺陷弛豫特性进而分析对多脉冲累积破坏的影响，在此基础上，基于强耦合多物理场作用机制建立瞬态缺陷诱导激光损伤机理模型。本项目的开展有助于弥补国内外关于损伤过程中材料特性变化研究的缺失，促进损伤阈值提升技术的发展。

稳态和瞬态缺陷使得光学元件抗激光损伤性能降低了两个量级。目前大量研究工作阐述各类稳态缺陷与激光损伤的关系，但是对于强激光诱导的具有一定弛豫时间的瞬态缺陷却少有报道。本项目以研究瞬态缺陷诱导激光损伤所涉及的关键技术、物理过程、基本原理等基础科学问题为目标开展相关研究工作。项目组首先自主构建了两类超快探测结构：（1）超高速采样皮秒时间分辨动态探测技术，（2）超快成像探测分析技术。.基于超高速采样皮秒时间分辨动态探测技术从损伤动态过程解析出发研究了瞬态缺陷对熔石英本征损伤过程的影响，包括单脉冲和多脉冲激光损伤过程，明确了瞬态缺陷对于等离子体形成和最终损伤的助推作用，并进一步深入研究了由于电致伸缩效应引起的纵向布里渊散射在瞬态缺陷形成过程中的影响，阐明本征损伤过程中瞬态缺陷的形成方式。.基于超快成像探测分析技术从损伤动态过程及光学性质变化出发研究瞬态缺陷对于透过率非线性下降及最终损伤形成的助推作用，进一步采用强激光辐照下在线谱分析技术证明了467nm的光致发光峰是强激光诱导的缺陷结构，由此出发分析瞬态缺陷的形成机理。稳态缺陷的存在导致其周围材料结构发生变化，强激光辐照下由于分子振动致使稳态缺陷附近形成了瞬态缺陷。.基于上述分析，明确瞬态缺陷与本征材料、稳态缺陷、强激光辐照之间的关联性，并获取瞬态缺陷弛豫特性进而明确它对重频多脉冲累积破坏的影响，在此基础上，建立瞬态缺陷诱导激光损伤机理模型。.项目执行过程中共发表学术论文10篇，其中SCI收录5篇，影响因子大于3的论文2篇，国内外核心期刊5篇，申请发明专利2项。项目圆满完成预期成果与技术指标。