Material anisotropy unveiled by random scattering of surface acoustic waves

Abstract

We consider launching a monochromatic surface acoustic wave packet on a large set of random scatterers. The interference of the multiple scatteredwaves creates a random pattern of ripples on the crystal surface that is recorded by optical interferometry. The Fourier transform of the amplitude and phase data of the measured wave field unveils the complete slowness curve, i.e., the wave-vector as a function of the propagation angle. A simple acoustic speckle model is proposed to explain this observation.