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.