Modeling of metal ablation induced by ultrashort laser pulses

International audienceAblation of metal targets by femtosecond laser pulses is studied numerically by using a one-dimensional hydrodynamic model. The model describes the absorption of laser radiation, electronic heat conduction, electron–phonon and electron–ion energy exchange and material motion. The temperature dependencies of heat capacities, thermal conductivities and electron–ion collision frequencies are taken into account. The ablation mechanisms are investigated in the intermediate laser fluence range, which is typical for surface processing applications. The employed hydrodynamic model shows that the ablation is driven by a total pressure gradient, which induces a compression (shock) wave propagating into the bulk and an unloading (rarefaction) wave leading to the material expansion. A phenomenon similar to the spallation is observed at fluences close to the ablation threshold. In addition, a fast overheating of the liquid material is observed, which may result into a decomposition of the material to a mixture of gas and droplets. The calculated initial conditions for plasma plume expansion are presented