Abstract The demand for higher throughput in the processing of materials with ultra-short pulsed lasers has motivated studies on the use of double pulses (DP). It has been observed in such studies that at relatively high time delays between the two pulses, the ablated volume is lower than that for a single pulse (SP). This has been attributed to the shielding of the second pulse and the re-deposition of the material removed by the first pulse. The investigation of re-deposition in copper with the aid of atomistic simulations is the main objective of this study. Nevertheless, a computational investigation of SP-ablation and experimental measurement of the SP-ablation depths and threshold fluence are also covered. The applied computational apparatus comprises a combination of molecular dynamics with the two-temperature model and the Helmholtz wave equation. The analysis of the simulation results shows that the derived quantities like the SP-ablation threshold fluence and the ratio of DP-ablation depth to SP-ablation depth are in agreement with the experimental values. An important finding of this study is that the characteristics of the re-deposition process are highly dependent on the fluence.

中文翻译：

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单脉冲和双脉冲金属超短脉冲激光烧蚀的原子模拟：再沉积现象的研究

摘要 用超短脉冲激光加工材料时对更高产量的需求激发了对双脉冲 (DP) 使用的研究。在此类研究中已经观察到，在两个脉冲之间相对较高的时间延迟下，消融体积低于单个脉冲 (SP) 的消融体积。这归因于第二个脉冲的屏蔽和由第一个脉冲去除的材料的重新沉积。借助原子模拟研究铜中的再沉积是本研究的主要目标。尽管如此，也涵盖了 SP 消融的计算研究和 SP 消融深度和阈值注量的实验测量。应用的计算设备包括分子动力学与双温度模型和亥姆霍兹波动方程的组合。对仿真结果的分析表明，SP-消融阈值注量和DP-消融深度与SP-消融深度之比等导出量与实验值一致。本研究的一个重要发现是再沉积过程的特征高度依赖于注量。