Negative-Refractive-Index Transmission-Line Metamaterials and Electromagnetic Applications

George V. Eleftheriades, Department of Electrical and Computer Engineering, University of Toronto

Recently there has been renewed interest in man-made materials with electromagnetic properties that cannot be found in nature. Therefore, these materials are referred to as "metamaterials" ("meta" means "beyond" in Greek). This lecture addresses metamaterials that can support negative refraction of electromagnetic waves. For example, the feasibility of media that simultaneously exhibit negative permittivity and negative permeability, hence a negative refractive index, has been known since the sixties. However, it is only recently that people discovered how to make them. 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 waves become focused on a point instead of diverging outwards, thus suggesting the implementation of lenses with flat surfaces.

In this seminar, first the fundamental properties of NRI metamaterials will be reviewed. Subsequently, it will be demonstrated that NRI metamaterials can be synthesized using planar networks of loaded transmission lines. The resulting metamaterials can be easily constructed using embedded capacitors and inductors. Since no resonators are explicitly involved, they offer wide operating bandwidths. Based on this approach, microwave NRI metamaterial lenses that can resolve details beyond the classical diffraction limit will be presented. Moreover, a number of useful antenna and microwave devices, enabled by such negative-refraction metamaterials will be demonstrated. These enabling materials and devices can find applications in diverse areas such as wireless communications, defense, and medical imaging.

The P/T Colloquium is
typically held each
Thursday, 3:45–5:00 PM.
Refreshments are served
at 3:15 PM.