An array of long metallic wires (the so-called “wire medium”) is typically associated with the concepts of artificial plasma and negative effective permittivity (e.g. J. Pendry, A. J. Holden, W. J. Stewart, and I. Youngs, Phys. Rev. Lett., 76, 4773, 1996). However, due to the emergence of strong nonlocal effects in the long wavelength limit (M. G. Silveirinha and C. A. Fernandes, IEEE Trans. Microw. Theory and Tech., vol. 53, p. 1418-1430, 2005, and C. R. Simovski and P. A. Belov, Phys. Rev. E, 70, 046616, 2004), the electrodynamics of such materials may be much richer than the “artificial plasma” simplistic description.

In a recent work (M. G. Silveirinha and C. A. Fernandes, Phys. Rev. B, 78, 033108, 2008), we have theoretically shown that unlike what is typically assumed, an array of crossed nonconnected metallic wires may interact with electromagnetic waves as a material with an extreme positive index of refraction, and not as material with negative permittivity. It was demonstrated that due to the anomalous interaction between crossed wires, the index of refraction may be made arbitrarily large, and depends mostly on the density of wires (number of wires per unit of volume). Such effect has good tolerance to metallic loss and is observed over a very wide frequency band due to its nonresonant nature. These extraordinary properties may enable the miniaturization of microwave and optical devices and the realization of ultra-subwavelength waveguides.

Recently, we have fabricated a prototype of the structured material using a layer by layer design and printed circuit techniques (M. G. Silveirinha, Carlos A. Fernandes, Jorge R. Costa, and Carla R. Medeiros, Appl. Phys. Lett., 93, 174103, 2008). In this talk, we will report the experimental demonstration of the anomalous properties of the metamaterial at microwaves, highlight the physical mechanisms inherent to the extreme values of the index of refraction, and discuss some potential applications and our ongoing work in this topic