Impedance-Matched, Double-Zero Optical Metamaterials Based on Weakly Resonant Metal Oxide Nanowires

Diego Abujetas,Ramón Paniagua-Domínguez,José Sánchez-Gil

doi:10.3390/photonics5020007

Diego Abujetas, Ramón Paniagua-Domínguez + Show 1 more

Open Access

https://doi.org/10.3390/photonics5020007

Copy DOI

Abstract

Artificial optical metamaterial with a zero index of refraction holds promise for many diverse phenomena and applications, which can be achieved with vacuum (or related) surface impedance and materials in the optical domain. Here, we propose simple metal-oxide nanorods as meta-atoms on the basis of an effective medium approach, based on their weak overlapping (electric/magnetic) resonances. We thus studied the optical properties of TiO 2 nanowire arrays with a high-filling fraction through their photonic band structure, which exhibits a double-degeneracy point without a band gap at the center of the Brillouin zone. Various configurations are considered that reveal their performance over a reasonable range of incident wave vectors as impedance-matched, double-zero, bulk (low-loss) metamaterials.

Highlights

In recent years, new phenomena have been observed in the field of metamaterials that would allow unprecedented control of the flow of electromagnetic waves, opening fascinating possibilities in different fields of physics and engineering
One approach has relied on high-index all-dielectric photonic crystals [15,30,31], exploiting the emergence of an accidental-degeneracy-induced Dirac point at the center of the Brillouin zone, which leads to an effective double-zero metamaterial (DZM) behavior [15]
We have extended the effective medium theory of magnetodielectric composites developed for cylinders or spheres, [58] which reduces in the quasi-static limit to the Maxwell–Garnett theory

Summary

Introduction

New phenomena have been observed in the field of metamaterials that would allow unprecedented control of the flow of electromagnetic waves, opening fascinating possibilities in different fields of physics and engineering. As is known, supercoupling effects, such as a perfect conductor slab or a waveguide filled with material with high Z values (where both ε and μ neither match nor approach zero with the same dispersion profile) can arise at specific configurations [9,10,11,27,36] In this regard, one approach has relied on high-index all-dielectric photonic crystals [15,30,31], exploiting the emergence of an accidental-degeneracy-induced Dirac point at the center of the Brillouin zone, which leads to an effective DZM behavior [15]. We propose dielectric nanorods with a lossless, moderately large dielectric function ε (as is the case of metal oxides), made of materials that can potentially span the whole visible range, at the expense of high-filling fractions, as excellent candidates for the meta-atoms of such impedance-matched, optical DZMs, revealing numerically their remarkable performance as DZM supercoupling devices in two dimensions based on arrays of titanium oxide nanowires

An Effective Medium Approach

Numerical Calculations

Conclusions