Localization length calculations in alternating metamaterial-birefringent disordered layered stacks

TL;DR

This paper investigates how replacing isotropic layers with negative-index metamaterials in layered stacks improves light localization across a broad wavelength range, reducing Brewster anomalies and enhancing broadband reflection properties.

Contribution

It introduces a novel approach using negative-index metamaterials to significantly enhance localization length and suppress Brewster anomalies in layered disordered stacks.

Findings

Localization length depends linearly on wavelength in the studied range.

Negative-index metamaterials reduce Brewster anomalies by over two orders of magnitude.

The localization enhancement is robust against different types of thickness and refractive-index disorder.

Abstract

A detailed theoretical and numerical analysis of the localization length in alternating metamaterial-birefringent random layered stacks, under uncorrelated thickness-disorder, has been performed. Similar structures have recently been reported to suppress the Brewster delocalization for $\it{p}$-polarized light, when "standard" isotropic layers (with positive index of refraction) are considered instead of metamaterial layers, providing a generic means to produce polarization-insensitive, broadband reflections. However, this enhancement of localization is valid for short wavelengths $\lambda$ compared to the mean layer thickness $a_0$. At higher wavelengths, we recover the Brewster anomalies for $\it{p}$-polarized states impeding a remarkable localization of light. To achieve a better localization for a wider range of wavelengths, we replaced the conventional isotropic layers by negative-index metamaterials presenting low losses and constant index of refraction over the near-infrared range. As a result, our numerical calculations exhibit a linear dependence of the localization length with $\lambda$ (in the region $5 <\lambda/a_0 < 60$) reducing the Brewster anomalies in more than two orders of magnitude with respect to the standard isotropic scheme at oblique incidence. This enhancement of localization is practically independent of the thickness disorder kind and is also held under weak refractive-index disorder.