Electromagnetic wave propagation through a wire array composite

Abstract

We consider the propagation of electromagnetic fields (EMF) through a composite dielectric medium supporting an array of parallel metal wires. The Maxwell-Garnett approximation has been previously used to describe the dielectric properties of such media. We show that, in addition to an effective dielectric constant, the medium also has an effective diamagnetic permeability associated with electric currents induced in the wires. We present a self-consistent model that allows for evaluation of the properties of EMF propagating along the wire length. Results from this model are in agreement with measurements of the infrared absorption of an array of 10-μm diameter, parallel indium wires in a glass matrix. We obtain a $k^{1/2}$ absorption dependence in the far-infrared $(k<\mathrm{}60\mathrm{}{\mathrm{cm}}^{\mathrm{-}1}),$ and a $k^2$ dependence due to losses in the glass matrix at higher frequencies. We also find that the reflectance is low in comparison to the bulk metal. If interwire effects are neglected, the EMF’s velocity of propagation is given by ${c/n}_i,$ where $n_i$ is the insulator refractive index, regardless of the metal volume fraction. For self-supported arrays ${(n}_i=1),$ we have verified experimentally that the velocity of propagation in the array is equal to the velocity of light in free space.