Interplay between localization and absorption in disordered waveguides

TL;DR

This paper uses ab-initio simulations to explore how absorption and localization influence wave transport in disordered waveguides, revealing a universal saturation of the diffusion coefficient and supporting the use of self-consistent localization theory.

Contribution

It demonstrates the non-zero saturation of the diffusion coefficient in absorbing disordered media and validates the self-consistent theory of localization in this context.

Findings

Diffusion coefficient saturates at a finite value in absorbing media.

Wave interference causes deviations from classical diffusion.

Self-consistent theory accurately describes the saturation regime.

Abstract

This work presents results of ab-initio simulations of continuous wave transport in disordered absorbing waveguides. Wave interference effects cause deviations from diffusive picture of wave transport and make the diffusion coefficient position- and absorption-dependent. As a consequence, the true limit of a zero diffusion coefficient is never reached in an absorbing random medium of infinite size, instead, the diffusion coefficient saturates at some finite constant value. Transition to this absorption-limited diffusion exhibits a universality which can be captured within the framework of the self-consistent theory (SCT) of localization. The results of this work (i) justify use of SCT in analyses of experiments in localized regime, provided that absorption is not weak; (ii) open the possibility of diffusive description of wave transport in the saturation regime even when localization effects are strong.