Spatio-Temporal Imaging of Light Transport in Highly Scattering Media under White Light Illumination

TL;DR

This paper introduces a passive, high-resolution method to image light transport in scattering media by measuring Green's functions, enabling detailed analysis of diffusion and localization phenomena.

Contribution

It presents a novel passive interferometric technique to map the spatio-temporal Green's matrix in scattering media, revealing diffusion anisotropy and local diffusion properties.

Findings

Quantitative imaging of diffusion constant with few transport mean free paths resolution

Detection and quantification of anisotropic light diffusion

Potential applications in biomedical imaging and fundamental physics

Abstract

Imaging the propagation of light in time and space is crucial in optics, notably for the study of complex media. We here demonstrate the passive measurement of time-dependent Green's functions between every point at the surface of a strongly scattering medium by means of low coherence interferometry. The experimental access to this Green's matrix is essential since it contains all the information about the complex trajectories of light within the medium. In particular, the spatio-temporal spreading of the diffusive halo and the coherent backscattering effect can be locally investigated in the vicinity of each point acting as a virtual source. On the one hand, this approach allows a quantitative imaging of the diffusion constant in the scattering medium with a spatial resolution of the order of a few transport mean free paths. On the other hand, our approach is able to reveal and quantify the anisotropy of light diffusion, which can be of great interest for optical characterization purposes. This study opens important perspectives both in optical diffuse tomography with potential applications to biomedical imaging and in fundamental physics for the experimental investigation of Anderson localization.