Weak Localization and Coherent Backscattering of Photons in Disordered Media

TLDR

Coherent backscattering of waves by a disordered scattering medium underlies weak localization. The study aims to directly observe weak localization of photons using visible light in suspensions of submicron polystyrene spheres. This was achieved by illuminating concentrated aqueous suspensions of submicron‑size polystyrene spheres with visible light. The scattered intensity is enhanced by up to 75 % within a narrow backscattering cone whose aperture inversely scales with the light mean‑free path controlled by sphere concentration, and the influence of polarization and particle size is discussed.

Abstract

Coherent backscattering of waves by a disordered scattering medium is responsible for weak localization. We have directly observed this effect for the first time using visible light and concentrated aqueous suspensions of submicron-size polystyrene spheres. The scattered intensity is found enhanced by up to 75% within a narrow cone centered at the backscattering direction. As predicted by theory, the aperture of the cone is inversely proportional to the light mean-free path; the latter was controlled by the concentration of spheres. The importance of light polarization and particle size is discussed.