Melting of gold by ultrashort laser pulses: Advanced two-temperature modeling and comparison with surface damage experiments

TL;DR

This study combines experimental laser damage threshold measurements with advanced two-temperature modeling to understand ultrafast laser-induced melting of gold, highlighting the importance of electron dynamics and coupling parameters.

Contribution

It introduces a comprehensive two-temperature model that accurately predicts gold melting thresholds under various ultrashort laser pulses, considering electron response complexities.

Findings

A specific model parameter set matches all experimental damage thresholds.

Electron-lattice coupling rate and ballistic electron effects are critical for accurate modeling.

Damage thresholds depend on laser intensity and electron participation in optical response.

Abstract

The ultrafast laser-induced solid-liquid phase transition in metals is still not clearly understood and its accurate quantitative description remains a challenge. Here we systematically investigated, both experimentally and theoretically, the melting of gold by single femto- and picosecond near-infrared laser pulses. Two laser systems with wavelengths of 800 and 1030 nm and pulse durations ranging from 124 fs to 7 ps were used and the damage and ablation thresholds were determined for each irradiation condition. The theoretical analysis was based on two-temperature modeling. Different expressions for the electron-lattice coupling rate and contribution of ballistic electrons were examined. In addition, the number of free electrons involved in the optical response is suggested to be dependent on the laser intensity and the influence of the fraction of involved electrons on the damage threshold was investigated. Only one combination of modelling parameters was able to describe consistently all the measured damage thresholds. Physical arguments are presented to explain the modeling results.