Transmission of evanescent wave modes through a slab of DNG material

Recent developments have made it possible to construct materials that behave in the millimeter and higher frequency regimes as if they have negative relative permittivity and permeability. As a result exotic-seeming wave-propagation properties that have been largely ignored since first predicted have become interesting. We review a recent claim that the initial decay in amplitude of evanescent plane-wave components of a signal in free space can be restored upon entry into an /spl epsiv/<0, /spl mu/<0 double negative (DNG) medium. We find, in a case study of a DNG medium with realizable parameters, that there is a minimal slab width d beyond which the field amplitude of any signal with nonzero bandwidth will decay with increasing d.