Crossover from renormalized to conventional diffusion near the 3D Anderson localization transition for light

TL;DR

This paper investigates how light transport transitions from anomalous to conventional diffusion in strongly scattering 3D media, revealing subdiffusive behavior and a crossover influenced by near-field effects, challenging the possibility of Anderson localization.

Contribution

It provides experimental evidence of a crossover from anomalous to slow diffusive light transport near the Anderson transition in 3D disordered media.

Findings

Observation of subdiffusive transport at early times

Identification of a crossover to slow diffusion at long times

Near-field coupling prevents Anderson localization in 3D

Abstract

We report on anomalous light transport in the strong scattering regime. Using low-coherence interferometry, we measure the reflection matrix of titanium dioxide powders, revealing crucial features of strong optical scattering which can not be observed with transmission measurements: (i) a subdiffusive regime of transport at early times of flight that is a direct consequence of predominant recurrent scattering loops, and (ii) a crossover to a conventional, but extremely slow, diffusive regime at long times. These observations support previous predictions that near-field coupling between scatterers prohibits Anderson localization of light in three-dimensional disordered media.