Resonant-light diffusion in a disordered atomic layer

TL;DR

This study experimentally investigates light diffusion in a dense, disordered atomic layer, revealing diffusion behavior and waveguiding effects, supported by models and simulations, advancing understanding of light-matter interactions in complex media.

Contribution

It provides experimental evidence of light diffusion and waveguiding in a dense atomic layer, supported by simple geometrical models and numerical simulations.

Findings

Light diffusion occurs in dense atomic layers with multiple scattering.

Detuned light exhibits behavior akin to a graded-index waveguide.

Models and simulations successfully reproduce experimental observations.

Abstract

Light scattering in dense media is a fundamental problem of many-body physics, which is also relevant for the development of optical devices. In this work we investigate experimentally light propagation in a dense sample of randomly positioned resonant scatterers confined in a layer of sub-wavelength thickness. We locally illuminate the atomic cloud and monitor spatially-resolved fluorescence away from the excitation region. We show that light spreading is well described by a diffusion process, involving many scattering events in the dense regime. For light detuned from resonance we find evidence that the atomic layer behaves as a graded-index planar waveguide. These features are reproduced by a simple geometrical model and numerical simulations of coupled dipoles.