Atomistic insight on temperature-dependent laser induced ultrafast thermomechanical response in aluminum film

Laser-induced ultrafast thermomechanical responses significantly impact ablation behaviors. Previous studies have focused on experimental observations, offering limited insights into the atomic phase transition process. This study explores the thermomechanical response of aluminum film to temperature changes using Molecular Dynamics coupled Two-Temperature Model (MD-TTM) and pump-probe imaging. The experimental results align closely with the simulations. In the simulations, the higher initial temperature tends to confine the heat to surface layer, creating regions of high potential energy. This confinement effect leads to accelerated surface melting, as evidenced by the more rapid decrease in reflectivity captured through ultrafast imaging. As the initial temperature increases from 300 K to 500 K, the stress distribution calculations show more pronounced surface spallation and reduced interior fractures. This alteration may impede thermal conduction from the surface to the interior. Consequently, the surface's enhanced thermomechanical response lowers the ablation threshold of the aluminum film by approximately 10 % and results in a significantly flatter ablation crater. In our opinion, integrating full-size MD-TTM simulations with ultrafast imaging provides deeper atomistic insights into the dynamics of ultrafast heat and mass transfer, which is crucial for improving processing quality and expanding technological capabilities.