Experimental Observation of a Fundamental Length Scale of Waves in Random Media

TL;DR

This paper reports the experimental observation of a fundamental length scale in wave transport through random media, revealing a new scaling behavior of wave branching and freak wave formation in weakly scattering environments.

Contribution

It provides the first experimental validation of a predicted fundamental length scale associated with wave fluctuations in random media, extending understanding beyond traditional mean free path concepts.

Findings

Scintillation index effectively assesses branching length scaling.

Experimental data confirms the existence of a new fundamental length scale.

Scaling range exceeds predictions from random caustics statistics.

Abstract

Waves propagating through a weakly scattering random medium show a pronounced branching of the flow accompanied by the formation of freak waves, i.e., extremely intense waves. Theory predicts that this strong fluctuation regime is accompanied by its own fundamental length scale of transport in random media, parametrically different from the mean free path or the localization length. We show numerically how the scintillation index can be used to assess the scaling behavior of the branching length. We report the experimental observation of this scaling using microwave transport experiments in quasi-two-dimensional resonators with randomly distributed weak scatterers. Remarkably, the scaling range extends much further than expected from random caustics statistics.