Light, a random walker? - Arthur Goetschy (Institut Langevin, ESPCI Paris)

How do waves such as light or sound propagate through fog, paint, or biological tissue? For decades, this process has been described in terms of the diffusion of wave intensity. However, this picture misses an essential ingredient: interference between distinct scattering paths. In this talk, we will explore two situations in which interference profoundly alters wave transport. In the first part, we will introduce a new propagation equation that describes how specially shaped waves, such as open transmission channels created using wavefront-shaping techniques, evolve inside scattering media. This provides access to the spatial structure of transport beyond the conventional diffusion picture. In the second part, rather than shaping the wave, we will shape the medium itself. We will show how strong spatial correlations can create pseudogaps and dramatically suppress wave transport, leading to an Anderson-type transition with intriguing connection to percolation. This effect will be illustrated for vector light propagating through three-dimensional disordered media.

Contact: Dorian Bouchet