Laser Ultrasonics in High Pressure Research: from Measurements of Material Parameters towards Imaging of its Inhomogeneity and Structural Transitions

Knowledge of pressure-dependences of sound velocities and elastic moduli of liquids and solids and understanding of the material texturing, plastic deformation and convection with increasing pressure is of extreme importance for a few branches of natural sciences such as condensed matter physics, physics of the Earth, seismology and planetology, as well as for monitoring of earthquakes, tsunamis or nuclear weapons tests. Starting 2008 lasers have been increasingly applied for the generation and detection of the bulk acoustic waves in the materials subjected to high pressures in diamond anvil cells (DAC). Until now it was demonstrated that subnanosecond, femtosecond and picosecond laser pulses can be applied for the generation of compression/dilatation and shear bulk acoustic waves and bulk acoustic waves skimming along the interfaces between different materials confined in a DAC. Optical monitoring of the propagation of these waves provides information on the sound velocities and sound attenuation in materials under high pressures.