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通过激光损伤实验,系统分析了传统研磨抛光加工工艺中表面杂质、刻蚀时间、亚表层缺陷和划痕宽深比对熔石英元件激光损伤阈值的影响。结果表明:擦洗后熔石英元件的激光损伤阈值为21.6J/cm~2,未经擦洗的元件的激光损伤阈值为11.28J/cm~2,受表层杂质影响激光损伤阈值大幅度降低,而有缺陷位置处的激光损伤阈值明显比无缺陷位置处的低。刻蚀时间的增加会使工件表面粗糙度和缺陷尺寸逐渐增大,导致光学元件激光损伤阈值大幅度下降,因此需要合理选择化学刻蚀时间。亚表层缺陷会对入射光场产生调制作用,造成局部区域反射光、散射光及入射光相互叠加,最终导致材料破坏而产生激光损伤。随着刻蚀时间的增加,划痕的宽深比会逐渐增大,可以逐渐减弱划痕对光场的调制作用,从而降低激光损伤发生的概率。
Through laser damage experiment, the influence of surface impurity, etching time, subsurface defect and width-to-depth ratio of scratches on the laser damage threshold of fused silica was systematically analyzed. The results show that the laser damage threshold of fused silica is 21.6J / cm ~ 2 after scrubbing, the damage threshold of non-scrubbed laser is 11.28J / cm ~ 2, the laser damage threshold is greatly reduced by surface impurities, The laser damage threshold at the defect location is significantly lower than at the defect-free location. The increase of etching time will make the surface roughness and defect size of the workpiece gradually increase, resulting in a sharp drop in the laser damage threshold of the optical component. Therefore, the chemical etching time needs to be properly selected. Sub-surface defects can modulate the incident light field, resulting in superposition of reflected light, scattered light and incident light in local areas, resulting in material damage and laser damage. With the increase of etching time, the width-to-depth ratio of scratches will gradually increase, which can gradually reduce the modulation effect of scratches on the light field, thus reducing the probability of laser damage.