In this study, we use a time-resolved pump-probe shadowgraph technique to investigate the evolution characteristics of filamentary damage in bulk fused silica induced by a nanosecond pulse at 532 nm. The pump laser focuses on the front surface of sample and filamentary damage appears independently in the middle of sample. The whole damage process can be divided into single filament (SF), double filaments (DFs), and long filament (LF) successively. At the same time, the improved moving focus model is proposed by taking into account the temporal shape of the laser pulse and the laser is blocked and reflected by plasma at the critical density. It is in good agreement with the experimental result of filamentary damage process and helps to explore the mechanism of laser-induced filamentary damage in nanosecond regime.

中文翻译：

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532 nm纳秒激光辐照熔融石英的丝状损伤

在这项研究中，我们使用时间分辨的泵浦探针阴影图技术来研究由532 nm的纳秒脉冲引起的块状熔融石英中丝状损伤的演变特征。泵浦激光聚焦在样品的前表面上，丝状损伤独立出现在样品的中间。整个损坏过程可以依次分为单丝（SF），双丝（DFs）和长丝（LF）。同时，通过考虑激光脉冲的时间形状和临界密度下的等离子体对激光的阻挡和反射，提出了改进的移动焦点模型。这与丝状损伤过程的实验结果非常吻合，有助于探讨纳秒范围内激光引起的丝状损伤的机理。