Eur. Phys. J. Plus (2015) 130: 50
https://doi.org/10.1140/epjp/i2015-15050-4

Regular Article

Metamaterial composed of coated nano-spheres at infrared frequencies

Department of Physics, Faculty of Science, Arak University, 8349-8-38156, Arak, Iran

^* e-mail: H-Sadeghi@araku.ac.ir

Received: 25 November 2014
Revised: 3 February 2015
Accepted: 11 February 2015
Published online: 26 March 2015

Abstract

A negative index of refraction in a three-dimensional collection of coated nano-spheres is observed in the terahertz (THz) spectral region. This negative-index metamaterial is a binary composite of two different types of coated nano-spheres (SiO₂@SiC/SiO₂@AZO); in one type SiO₂ spheres coated with a semiconductor (SiC) nano-shell and in another one, nano-shells made of a plasmonic material (AZO). The effective medium parameters derived by extended Maxwell-Garnett (EMG) effective medium theory by specifying the Mie resonances of the coated nano-spheres in the binary composite. The results are supplemented with frequency band structure and transmission curves, calculated by an accurate electromagnetic multiple-scattering technique. The predictions of the EMG theory are in agreement with those of the multiple-scattering technique, providing the effective medium approximation a helpful guide for the experimental works in this field.