Focusing in Transmission-Line Negative-Refractive-Index Metamaterials

Recently there has been renewed interest in man-made materials with electromagnetic properties that cannot be found in nature. Therefore these artificial materials are referred to as “metamaterials” (“meta” means “beyond” in Greek). This presentation addresses metamaterials characterized by a negative index of refraction. The feasibility of media that simultaneously exhibit negative permittivity and negative permeability, hence a negative index of refraction, has been known since the sixties. However it is only recently that people discovered how to make them in the laboratory at microwave frequencies. In such negative-refractive-index (NRI) or “left-handed” metamaterials, waves can be thought of as propagating backwards instead of forwards. When interfaced with conventional dielectric materials, incident spherical waves become focused on a point instead of diverging outwards, thus suggesting the implementation of lenses with flat surfaces.