Ionization dynamics of submicron-sized clusters in intense ultrafast laser pulses

TL;DR

This paper studies how intense ultrafast laser pulses ionize submicron clusters, revealing the roles of Mie scattering, nanofocusing, and plasma shielding in the ionization process, which is crucial for laser-cluster experiments and nanomachining.

Contribution

It provides a detailed analysis of ionization dynamics in submicron clusters using Mie calculations and particle-in-cell simulations, highlighting the effects of internal field localization.

Findings

Nanofocusing causes rear-side ionization hotspots at lower intensities.

Plasma shielding prevents further ionization at higher intensities.

Ionization dynamics depend on the interplay of pulse propagation and cluster size.

Abstract

Submicron-sized targets are found in intense laser-cluster interaction experiments and laser-based material processing. Here we investigate the internal field localization due to Mie scattering and its effect on ionization dynamics in submicron-sized clusters using Mie calculation and particle-in-cell simulations. As a result of intertwined processes of pulse propagation and ionization, sub-micron nanofocusing dominates at lower intensity and gives rise to an ionization hotspot at the rear of the targets while plasma shielding wins over at a higher intensity, stopping further rear side ionization. As ionization is often the precursor of other processes, understanding the ionization dynamics of ultrafast laser pulses with wavelength-sized nanostructure can be relevant for intense laser-cluster experiments and femtosecond laser micro/nanomachining.