An ultrafast pump-probe shadowgraph imaging system and a laser induced breakdown spectroscopy (LIBS) system were used to investigate the modulation and mechanism of shockwaves of nickel (Ni) and aluminum (Al) induced by femtosecond laser double-pulse. With a suitable pulse delay, the bulge in the axial direction of the shockwave can be effectively eliminated and the shockwave expanded evenly in a hemispheric structure. The radial expansion distance of shockwaves of Ni and Al increased by 30% and 50% respectively with double-pulse excitation. The strong coupling of laser with liquid layer and plasma shielding effect were responsible for the enhancement of shockwaves within different regimes of pulse delay. Different enhancement trends were observed for the shockwaves of Ni and Al in the initial regime of pulse delay. Further study indicated that the reduced ablation volume of Al counteracted the enhancement effect of double-pulse on plasma and shockwave and it was the dominant me...

中文翻译：

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飞秒激光双脉冲在金属上引起的冲击波的调制及其机理

为了研究飞秒激光双脉冲引起的镍（Ni）和铝（Al）冲击波的调制及其机理，采用了超快泵浦探针阴影图成像系统和激光诱导击穿光谱（LIBS）系统。通过适当的脉冲延迟，可以有效地消除冲击波的轴向隆起，并且冲击波在半球形结构中均匀地扩展。在双脉冲激发下，镍和铝的冲击波的径向膨胀距离分别增加了30％和50％。激光与液层的强耦合和等离子体屏蔽效应是在不同脉冲延迟范围内增强冲击波的原因。在脉冲延迟的初始状态下，Ni和Al的冲击波观察到不同的增强趋势。