Revealing sub-{\mu}m inhomogeneities and {\mu}m-scale texture in H2O ice at Megabar pressures via sound velocity measurements by time-domain Brillouin scattering

TL;DR

This study employs time-domain Brillouin scattering to achieve sub-micrometer resolution in depth-profiling polycrystalline ice under Megabar pressures, revealing inhomogeneities and texture with high spatial precision.

Contribution

It demonstrates the use of picosecond ultrasonic interferometry for three-dimensional imaging of ice's elastic inhomogeneities at unprecedented resolution.

Findings

Sub-micrometer inhomogeneities in ice detected

Inhomogeneities and texture characterized in-depth and laterally

Potential for 3D imaging of transparent polycrystalline materials

Abstract

Time-domain Brillouin scattering technique, also known as picosecond ultrasonic interferometry, which provides opportunity to monitor propagation of nanometers to sub-micrometers length coherent acoustic pulses in the samples of sub-micrometers to tens of micrometers dimensions, was applied to depth-profiling of polycrystalline aggregate of ice compressed in a diamond anvil cell to Megabar pressures. The technique allowed examination of characteristic dimensions of elastic inhomogeneities and texturing of polycrystalline ice in the direction normal to the diamond anvil surfaces with sub-micrometer spatial resolution via time-resolved measurements of variations in the propagation velocity of the acoustic pulse traveling in the compressed sample. The achieved two-dimensional imaging of the polycrystalline ice aggregate in-depth and in one of the lateral directions indicates the feasibility of three-dimensional imaging and quantitative characterization of acoustical, optical and acousto-optical properties of transparent polycrystalline aggregates in diamond anvil cell with tens of nanometers in-depth resolution and lateral spatial resolution controlled by pump laser pulses focusing.