Breakdown of self-similarity in light transport

TL;DR

This study experimentally demonstrates a breakdown of self-similar light transport in scattering media, revealing complex scaling behaviors that challenge traditional diffusion classifications and have broad implications for understanding various transport phenomena.

Contribution

It provides the first experimental evidence of non-self-similar light propagation in isotropic, homogeneous media, highlighting the need for a richer framework beyond normal and anomalous diffusion.

Findings

Breakdown of self-similarity observed in light transport.

Control of this phenomenon via turbidity tuning.

Implications for understanding complex transport regimes.

Abstract

Transport processes underpin a multitude of phenomena, ranging from the propagation of atoms on lattices, to the mobility patterns of microorganisms and earthquakes, to name a few. The dynamics of these processes is very rich and key to understanding the complex nature of the underlying physics, but the way in which we classify them is often too simplistic to fully reflect this complexity. Here, we report on the experimental observation of a breakdown of self-similar propagation for light inside a scattering medium - a transport regime exhibiting different scaling rates for each spatial moment of the associated probability distribution. Notably, we show that this phenomenon arises for light waves even in the simple case of isotropic and homogeneous disorder, and can be controlled by tuning the turbidity of the system. These results support the idea that the traditional dichotomy between normal and anomalous diffusion is reductive and that a richer framework should be constructed based on the concept of self-similarity as this class of transport regimes may be far more common that it is currently believed. In addition, this insight can help understand scenarios where transport is dominated by rare propagation events, as in non-linear and active media, or more generally in other fields of research.