Laura Cobus (Institut Langevin) - Strong scattering and localization of classical waves : experimental investigations

Wave propagation in complex media, having been actively researched for several decades, remains at the frontier of science. One of the most interesting aspects of this field is that one can observe anomalous wave behaviour, i.e. behaviour that is different to what is expected in most situations. Most wave propagation through a medium of random scattering objects can be well-described by the diffusion approximation, in which interference effects between individual waves are unimportant. However, there are interference effects which exist nonetheless, and which must be explained with a more comprehensive theory of wave scattering. They can thus provide deeper insight into the nature of wave interaction with the microstructure of the medium. Perhaps the most extreme example of anomalous behaviour caused by interferences is Anderson localization, where waves are spatially ‘trapped’ in the medium due to the disorder of the scatterers. Such important departures from diffusion generally occur in the strong scattering regime, where the scatterer size is comparable to the wavelength. In this talk, we will discuss several experimental approaches which use ultrasound to search for anomalous effects in the strong scattering regime, and to uncover the elusive phenomenon of Anderson localization.