Investigation of ultrashort laser excitation of aluminum and tungsten by reflectivity measurements

TL;DR

This study measures the ablation threshold and reflectivity of aluminum and tungsten under ultrashort laser pulses, developing a simulation model to understand their transient thermodynamic and optical responses.

Contribution

It extends the understanding of laser-material interactions by analyzing ablation thresholds and reflectivity for metals under few-cycle pulses, incorporating detailed density of states in simulations.

Findings

Ablation threshold fluence remains constant across pulse durations.

Reflectivity measurements reveal energy deposition dynamics.

Simulations highlight the importance of density of states in tungsten.

Abstract

We determine the laser-induced ablation threshold fluence in air of aluminum and tungsten excited by single near-infrared laser pulses with duration ranging from 15 fs to 100 fs. The ablation threshold fluence is shown constant for both metals, extending the corresponding scaling metrics to few-optical-cycle laser pulses. Meanwhile, the reflectivity is measured providing access to the deposited energy in the studied materials on a wide range of pulse durations and incident fluences below and above the ablation threshold. A simulation approach, based on the two-temperature model and the Drude-Lorentz model, is developed to describe the evolution of the transient thermodynamic and optical characteristics of the solids (lattice and electronic temperatures, reflectivity) following laser excitation. The confrontation between experimental results and simulations highlights the importance of considering a detailed description and evolution of the density of states in transition metals like tungsten.