The impact of the substrate on the opto-thermal response of thin metallic targets following irradiation with femtosecond laser pulses

TL;DR

This study investigates how substrate materials influence the opto-thermal response of thin metallic films under femtosecond laser irradiation, highlighting the importance of substrate properties for optimizing laser processing.

Contribution

It demonstrates that substrate optical and thermophysical properties significantly affect thermal responses and damage thresholds in thin metal films, especially at smaller sizes.

Findings

Substrate properties alter thermal fingerprint of irradiated films.

Impact of substrate is more pronounced at smaller film sizes.

Different substrates lead to varied damage thresholds.

Abstract

Femtosecond pulsed lasers have been widely used over the past decades due to their capability to fabricate precise patterns at the micro- and nano- lengths scales. A key issue for efficient material processing is the determination of the laser parameters used in the experimental set ups. Despite a systematic investigation that has been performed to highlight the impact of every parameter independently, little attention has been drawn on the role of the substrate material on which the irradiated solid is placed. In this work, the influence of the substrate is emphasised for films of various thicknesses which demonstrates that both the optical and thermophysical properties of the substrate affect the thermal fingerprint on the irradiated film while the impact is manifested to be higher at smaller film sizes. Two representative materials, silicon and fused silica have been selected as typical substrates for thin films of different optical and thermophysical behaviour (gold and nickel) and the thermal response and damage thresholds are evaluated for the irradiated solids. The pronounced influence of the substrate is aimed to pave the way for new and more optimised designs of laser-based fabrication set ups and processing schemes.