Nanoscale subsurface dynamics of solids upon high-intensity femtosecond laser irradiation observed by grazing-incidence x-ray scattering

Abstract

Observing ultrafast laser-induced structural changes in nanoscale systems is essential for understanding the dynamics of intense light-matter interactions. For laser intensities on the order of 1014W/cm2, highly collisional plasmas are generated at and below the surface. Subsequent transport processes such as heat conduction, electron-ion thermalization, surface ablation, and resolidification occur at picosecond and nanosecond timescales. Imaging methods, e.g., using x-ray free-electron lasers (XFEL), were hitherto unable to measure the depth-resolved subsurface dynamics of laser-solid interactions with appropriate temporal and spatial resolution. Here we demonstrate picosecond grazing-incidence small-angle x-ray scattering (GISAXS) from laser-produced plasmas using XFEL pulses. Using multilayer (ML) samples, both the surface ablation and subsurface density dynamics are measured with nanometer depth resolution. Our experimental data challenges the state-of-the-art modeling of matter under extreme conditions and opens new perspectives for laser material processing and high-energy density science.Received 11 December 2021Accepted 23 May 2022DOI:https://doi.org/10.1103/PhysRevResearch.4.033038Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasHigh intensity laser-plasma interactionsHigh-energy-density plasmasPhysical SystemsPlasma sheaths & surfacesStrongly-coupled plasmasWarm-dense matterTechniquesHydrodynamicsLaser ablationParticle-in-cell methodsX-ray reflectivityX-ray scatteringPlasma PhysicsCondensed Matter, Materials & Applied Physics