Light Propagation in Oil-Immersed Weakly Disordered Glass

The propagation of light in disordered media is a rich and emerging topic of research [1], recently reinvigorated by the discovery of the regime of branched flow at light wavelengths [2]. The interest in this topic can be twofold: for fundamental physics, owing to the ubiquitous nature of branching for waves, and for conceiving new technologies for sensing applications. From the seminal works of Refs. [2], [3], light branching is a particular regime that appears before the better-known diffusion regime: to observe branching the refractive index spatial variation should occur over a scale much longer that the wavelength while the refractive index variation should be weak enough to induce small scattering. Such phenomenon in optics has been observed first in a thin soap membrane either with coherent [2] and incoherent light [3]. A recent numerical analysis shows the occurrence of light branching in thick media or multimode slab waveguides [4] and how wavefront shaping can be used to steer and control the branches. More recently, electrical tunability of light branches in liquid crystals has been also demonstrated experimentally [5].