Imaging of ablation dynamics by soft x-ray laser

A single-shot soft x-ray laser pulse was used as a probe to investigate the early stage of the laser ablation process on platinum caused by the femtosecond near-infrared pump pulse. From time-resolved interferometry, we observed the dilation of the ablation front on a scale of 10 nm in the picosecond region. In the reflective imaging, we found three distinct types of dynamical responses, depending on the radial position in the pump beam spot. These characteristic behaviors correspond to different laser fluence and were attributed to different ablation schemes: spallation, homogeneous nucleation, and fragmentation/vaporization, have been predicted from molecular dynamics simulation. (author)