Simulation of phase explosion in the nanosecond laser ablation of aluminum

Vaporization, spallation and phase explosion are considered to be the main mechanisms contributing to the nanosecond laser ablation of metals. The theory of homogeneous nucleation, together with the dynamics of target heating, allows a space-time resolved simulation of the phase explosion mechanism. The thermal phenomena occurring at the target surface are studied within the framework of a thermodynamic continuum approach. A 20 ns laser pulse of variable fluence and Gaussian time dependence was assumed. The temperature profile in the target external layers is studied through the heat diffusion equation. The vaporization from the surface is modeled assuming unsteady adiabatic expansion (UAE) of the vapor and a Monte Carlo (MC) method is used to describe the formation of liquid nanodroplets through phase explosion. Liquid nanodroplets in the ablated material are studied at different laser fluences. The size distribution of the nanodroplets formed in the phase explosion process is here reported and connections with experiments are discussed.