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摘要光学玻璃作为光学元器件的基本材料，目前已被广泛应用于各种光学器件。国内外众多科研工作者对激光致光学玻璃表面损伤问题进行了大量的理论和实验研究。光学玻璃表面裂纹是改变材料自身光场，从而影响元件的抗激光损伤能力的重要因素之一。 本文根据熔石英表面裂纹诱导激光损伤展开，基于光场理论和有限元方法，讨论微裂纹对入射光场的调制作用，对熔石英表面裂纹周围的光场分布进行数值模拟，初步探讨了熔石英入射表面与出射表面裂纹引起的光强增强效应，给出径向裂纹周围光场的分布，定量研究光场调制的光强增强因子和裂纹结构参数（裂纹角度、裂纹宽度以及裂纹深度）的关系，为场致损伤给出相应的理论参考。61094
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毕业论文关键词 表面裂纹 光场分布 PML 光强增强因子
Title Study of Enhancement Effects of Surface Cracks on Light Intensity Distribution at Optical Glass Surfaces
Abstract Many domestic and foreign research workers did a lot of theoretical and experimental research on the laser induced surface damage of optical glass problem. Surface cracks of optical glass is one important factor that it can change the material itself light field, thus affecting the ability of laser damage resistance element. Optical glasses, as the base material of optical components, are widely applied to various optical devices. A mass of theoretical and experimental studies on laser-induced surface damage of optical glasses have been carried out by many researchers. Surface cracks can modulate light field in materials, which play a significant role in lowering laser-induced damage threshold of optical glass. This paper was based on damage of fused silica induced by surface cracks. The theory of light field propagation and the finite element method were used to study the modulation of light field created by microcracks. First, light field distributions near fused silica surfaces were simulated. Then, light intensification effects generated by cracks at input and output surfaces were analyzed. The light intensity profiles in the vicinity of the planar radial cracks are showed. Third, the relationship between structure parameters(crack width, depth and orientation with the surface normal) of cracks and the light intensity enhancement factor was investigated quantitatively, and the results can provide theoretical reference for electric field induced damage.
Keywords Surface cracks Optical field distribution PML LIEF
目次
1引言1
1.1激光诱导光学玻璃的损伤1
1.1.1损伤的定义1
1.1.2体损伤和面损伤1
1.1.3亚表面缺陷损伤机制2
1.2国内外研究现状3
1.3本文工作4
2理论模型5
2.1物理模型5
2.1.1正入射和反入射6
2.1.2熔石英亚表面周围的电场7
2.2熔石英表面光场的有限元模拟8
2.2.1有限元法8
2.2.2理想匹配层9
2.2.3周期性边界条件9
2.2.4有限元模拟10
3裂纹对熔石英入射表面和出射表面处光场分布的调制作用11
3.1入射表面11
3.2出射表面14
结论18
致谢19
参考文献20
1 引言 光学玻璃作为光学元器件的基本材料，目前已被广泛应用于各种光学器件中，如光学窗口、反射镜以及各种膜的基底。而光学材料在加工制备过程中，由于工艺原因，如切割、研磨、抛光等，会在表面和亚表面形成很多类型的机械和化学缺陷，难以避免地会引入残留杂质和亚表面包裹物以及形状复杂、尺寸深度不同的裂纹，使各个玻璃表面存在差异[1,2]。在强激光系统中这些光学元件表面的微结构使光学玻璃表面附近的光场分布发生变化，局部区域光场得到增强源]自=751-·论~文"网·www.751com.cn/ ，严重影响了元件的抗激光损伤能力[3]。因此，深入研究亚表面缺陷在激光损伤光学玻璃中所起的作用对延长光学元件的使用寿命、提高高功率光学系统装置的负载能力有着重要意义[4]。