(Sub-)picosecond surface correlations of femtosecond laser excited Al-coated multilayers observed by grazing-incidence x-ray scattering

TL;DR

This study uses grazing-incidence x-ray scattering to observe ultrafast surface and subsurface structural changes in aluminum-coated multilayers caused by femtosecond laser pulses, providing insights into nanostructure formation and validation of extreme matter models.

Contribution

It demonstrates the capability of XFEL-based GISAXS to resolve nanometer-scale surface and subsurface dynamics with subpicosecond resolution in laser-irradiated multilayers, advancing understanding of laser-material interactions.

Findings

Differentiation of surface and subsurface dynamics

Validation of extreme condition simulation models

Potential for controlled nanostructure fabrication

Abstract

Femtosecond high-intensity laser pulses at intensities surpassing $10^{14} \,\text{W}/\text{cm}^2$ can generate a diverse range of functional surface nanostructures. Achieving precise control over the production of these functional structures necessitates a thorough understanding of the surface morphology dynamics with nanometer-scale spatial resolution and picosecond-scale temporal resolution. In this study, we show that individual XFEL pulses can elucidate structural changes on surfaces induced by laser-generated plasmas, employing grazing-incidence small-angle x-ray scattering (GISAXS). Using aluminum-coated multilayer samples we can differentiate between ultrafast surface morphology dynamics and subsequent subsurface density dynamics, achieving nanometer-depth sensitivity and subpicosecond temporal resolution. The observed subsurface density dynamics serve to validate advanced simulation models depicting matter under extreme conditions. Our findings promise to unveil novel avenues for laser material nanoprocessing and high-energy-density science.