Mechanism of ultrashort laser ablation of metals: molecular dynamics simulation

A theoretical model is developed and a molecular dynamics simulation technique is applied for the description of ultrashort laser ablation of metals. The ablation of Al, Ni, and Fe using 0.1, 0.5 and 5 ps laser pulses at wavelengths of 248 and 800 nm is studied. The process is investigated at fluences up to 0.5 J/cm2. The analysis based on the temporal evolution of the ablation, the temperature, and the pressure distributions into the material reveals that a thermo-mechanical mechanism (spallation) takes place near the threshold. However, phase explosion is found to be the dominant mechanism of material removal at fluences higher than several hundreds of mJ/cm2. The influence of the laser parameters (wavelength and pulse duration) is obtained and discussed. The ablation depth as a function of the laser fluence and the ablation threshold value are evaluated and compared with the experimental data available. Good agreement between the theory and experiments is observed.