The dynamics of the melt pool induced by high power lasers in a metallic substrate is a complex manifestation of many competing thermophysical processes. Recent experimental results generated during the irradiation of metallic samples by 30 ps laser pulses are presented. The high power associated with these pulses (approx10 GW/cm~2) causes radiative ablation of the target material. Variation of experimental parameters leads to qualitative changes in the morphology of the resolidified melt zone, and several regimes of operation exhibit fractal features. These features provide substantial information on the time and length scales associated with the phase change processes, and provide a diagnostic tool for evaluating the nature of the laser-material interaction. A simplified model incorporating these fractal features is presented to facilitate calculations of the flow fields occurring within the melt pool.
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