Cherenkov radiation in a metamaterial comprised of coated wires

The electromagnetic field of a point charge moving in a "wire metamaterial" parallel to the wires is investigated. The metamaterial under consideration is a periodic structure of perfect conductors with a dielectric or magnetic coating. The spacing of the structure is assumed to be much less than the typical wavelengths; therefore, the structure can be described as an anisotropic medium that exhibits both frequency and spatial dispersions. In this paper, the general expressions for the field components have been obtained. A comparison with the charge field in a cold plasma has been performed. The charge is shown to radiate when its velocity is greater than a threshold determined by the wire coating parameters. The properties of the Cherenkov radiation in the metamaterial under consideration differ radically from those in an ordinary isotropic medium. In particular, the spectral density of the radiation energy decreases with the frequency. The maximum of the radiation pattern falls in the direction of the charge motion (if the losses in the medium are negligible) or in some close direction (if the losses are considered). For the ultrarelativistic case, the radiation pattern is very narrow, and the charge energy loss is small. (C) 2013 Optical Society of America