Liu Zhichao, Geng Feng, Li Yaguo, Cheng Jian, Yang Hao, Zheng Yi, Wang Jian, Xu Qiao
Appl Opt. 2018 Dec 10;57(35):10334-10341. doi: 10.1364/AO.57.010334.
The surface damage morphology of potassium dihydrogen phosphate (KDP) crystal under 351 nm nanosecond laser irradiation is studied, and the formation mechanisms of each damage type are discussed. There are three unique types of KDP surface damage, namely, crack, shell, and crater, under the fluence between 5 and 15 J/cm. The fracture feature of crack type damage indicates the pure mechanic process during laser exposure. Some cracks result in the upwarp of the material with a height of 0.1-0.5 μm. The shell is a most typical damage morphology with a proportion as large as about 80%. The transverse size of shell ranges from 5 to 82 μm, related to the fluence. The crater has a distinguished core structure related to the high-temperature process. The evidence of dehydration reaction is found in the core by energy dispersive spectrometer semiquantitative analysis. Internal morphology analysis with a focused ion beam suggests that the crack and shell damage originate from the surface or subsurface machining defects, while the crater damage is mainly due to material bulk defects.
研究了磷酸二氢钾（KDP）晶体在351 nm纳秒激光辐照下的表面损伤形貌，并讨论了每种损伤类型的形成机制。在5至15 J/cm的能量密度下，KDP表面存在三种独特的损伤类型，即裂纹、壳层和坑洼。裂纹型损伤的断裂特征表明激光辐照过程为纯机械过程。一些裂纹导致材料向上翘曲，高度为0.1 - 0.5μm。壳层是最典型的损伤形貌，比例高达约80%。壳层的横向尺寸为5至82μm，与能量密度有关。坑洼具有与高温过程相关的独特核心结构。通过能谱仪半定量分析在核心中发现了脱水反应的证据。聚焦离子束内部形貌分析表明，裂纹和壳层损伤起源于表面或亚表面加工缺陷，而坑洼损伤主要归因于材料体缺陷。
