Varying the effective refractive index to measure optical transport in random media

TL;DR

This paper presents a novel method to measure light transport properties in heterogeneous media by varying the effective refractive index through ambient pressure changes, confirming the effective medium concept in strongly scattering materials.

Contribution

The study introduces a spectrally resolved refractive index tuning technique to experimentally determine transport properties, linking frequency variation to effective medium theory in scattering media.

Findings

Intensity correlations measured via index tuning match theoretical predictions.

The diffusion constant is precisely determined and validated.

Effective medium concept is confirmed in strongly scattering materials.

Abstract

We introduce a new approach for measuring both the effective medium and the transport properties of light propagation in heterogeneous media. Our method utilizes the conceptual equivalence of frequency variation with a change in the effective index of refraction. Experimentally, we measure intensity correlations via spectrally resolved refractive index tuning, controlling the latter via changes in the ambient pressure. Our experimental results perfectly match a generalized transport theory that incorporates the effective medium and predicts a precise value for the diffusion constant. Thus, we directly confirm the applicability of the effective medium concept in strongly scattering materials.