Melting and thermal ablation of a silver film induced by femtosecond laser heating: A multiscale modeling approach

TL;DR

This study employs a multiscale simulation combining quantum mechanics, molecular dynamics, and two temperature models to analyze femtosecond laser-induced melting and ablation in silver films, revealing thresholds and mechanisms of phase change.

Contribution

It introduces an integrated multiscale modeling approach with ab initio derived parameters to accurately simulate laser-induced phase transitions in silver.

Findings

Identified laser fluence thresholds for melting and ablation.

Described thermal ablation caused by rapid expansion of superheated silver.

Provided insights into phase change mechanisms under femtosecond laser heating.

Abstract

The femtosecond laser pulse heating of silver film is investigated by performing quantum mechanics (QM), molecular dynamics (MD) and two temperature model (TTM) integrated multiscale simulation. The laser excitation dependent electron thermophysical parameters (electron heat capacity, electron thermal conductivity, and effective electron-phonon coupling factor) are determined from ab initio QM calculation, and implemented into TTM description of electron thermal excitation, heat conduction, as well as electron-phonon coupled thermal energy transport. The kinetics of atomic motion is modeled by MD simulation. Energy evolution of excited electron subsystem is described by TTM in continuum. The MD and TTM are coupled by utilizing the effective electron-phonon coupling factor. Laser heating with varying laser fluence is systematically studied to determine the thresholds of the homogeneous melting and ablation. The thermal ablation induced by faster expansion of locally and excessively superheated silver is reported. This paper provides a basis for interpreting the phase change process induced by laser heating, and facilitates the advancement of femtosecond laser pulse processing of material.