纳秒和飞秒激光烧蚀单晶硅的超快诊断

Ultra-fast diagnosis of monocrystalline silicon ablated by ns and fs laser

为了研究强激光烧蚀单晶硅的超快动力学过程,采用超快时间分辨光学诊断技术,对比研究了纳秒和飞秒脉冲激光烧蚀单晶硅样品表面的动态过程,获得了冲击波、等离子体和物质喷发的产生与演化过程的时间分辨图像。对于纳秒激光,当延迟时间为200ns^300ns时,观察到物质喷发现象出现,此时喷发物为气液混合物,当延迟时间为1060ns时,喷发物为小液滴;对于飞秒激光,当延迟时间为1ns^2ns时,观察到物质喷发现象出现,喷发物为等离子体。结果表明,在样品表面,纳秒激光与飞秒激光烧蚀单晶硅的动态过程有显著的不同,特别是物质喷发时间、喷发物的状态与尺寸;纳秒和飞秒激光辐照单晶硅表面引起的物质喷发都是不连续的,在激光烧蚀单晶硅引起表面物质喷发的过程中,不同的作用时间由不同的烧蚀机制主导。该结果对深入研究激光与单晶硅相互作用机制及激光刻蚀单晶硅等应用有一定帮助。

In order to study ultrafast dynamics of high power laser ablation of silica,the dynamic process of monocrystalline silicon ablated by nanosecond（ ns） and femtosecond（ fs） laser was investigated by the technology of ultrafast time-resolved optical diagnosis. The time-resolved shadowgraphs of the formation and evolution process of plasma expansion,material ejection and shock waves were obtained. For ns laser,material ejection occurs at 200 ns - 300 ns of delay time with gas-liquid mixture and at 1060 ns of delay time with droplet ejection. For fs laser,material ejection occurs at 1ns - 2ns of delay time with plasma. The result shows that the dynamic process of laser ablation is significantly different between by fs laser and by ns laser,especially the time of material ejection and the state and size of ejection particles. The results indicate that the process of material ejection induced by ns and fs laser is discontinuous and show that the material ejection is caused by different ablation mechanisms in different time. The results are helpful for the study of interaction mechanism of laser and silica,as well as laser etching monocrystalline silicon.