飞秒激光烧蚀铝靶产生喷射物的超快脉冲数字全息诊断

Ultra-fast pulsed digital holographic diagnosis of ejected material in femtosecond laser ablation of aluminum

采用脉冲数字显微全息技术,对50fs单脉冲激光烧蚀铝靶过程中的物质喷射以及等离子体演化的动态过程进行了实验研究,获得了高时空分辨的动态数字全息图.由全息图观察到了热弹力波引起的二次喷射现象,并且报道了大延迟下喷射物质对400nm探测光所引起的干涉条纹的反常移动现象.通过对全息图进行数字再现,得到了不同延迟下探测光穿过等离子体后的二维相位分布,并运用逆Abel变换算法获得了等离子体折射率以及等效电子密度的时空演化动态过程.根据实验以及计算所得到的有关于喷射物的光学性质,对喷射物的结构和成分进行了分析.

The dynamic process of material ejection and plasma evolution in single 50 fs laser pulse ablation of aluminum target is investigated using pulsed digital micro-holography, and highly temporally and spatially resolved dynamic digital holograms are obtained. The secondary material ejection induced by the thermoelastic wave is observed in the holograms, and at the same time, we firstly report the phenomenon of anomalous fringe shift at large time delays that results from the effect of the ejected material towards the probe beam of 400 nm wavelength. Through digital reconstruction, the two-dimensional phase shift distribution of the probe beam is obtained. By employing inverse Abel transform, we also obtained the dynamic process of spatial and temporal evolution of refractive index and free electron density distribution of the plasma. The structure and composition of the ejected material is analyzed according to its optical properties which are obtained through experiment and calculation.