Artificial dielectrics having refractive indices less than unity

Two types of artificial dielectric are examined; the first consists of an array of conducting rods and the second of a set of parallel conducting plates having perforations in the form of circular holes. Both these media are designed to operate for an incident electromagnetic wave, which is polarized so that its electric field is parallel to the conducting elements. It is found that the effective refractive index of such media is less than unity. An analysis of the propagation within these media gives results from which the effective refractive index may be calculated. The reflection which occurs at the interface between the medium and free space is also investigated.