The science of negative index materials

Metamaterials are designed to have structures that make available properties not found in Nature. Their unique properties (such as negative index of refraction, n) can be extended from GHz all the way to optical frequencies. We review the scaling properties of metamaterials that have been fabricated and give negative n and negative permeability, μ. It is found that most of the experimentally realized metamaterials have λ/a between 2 (THz and optical region) and 12 (GHz region), where λ is the operation wavelength and a is the size of the unit cell. The transmission losses for the experimental structures and the ratio λ/a for the simulated structures are presented. Finally, a comparison of the different metamaterial designs (fishnet, cut and/or continuous wires, and split-ring resonators and wires) is given