Dual-band negative-index metamaterials in the near-infrared frequency range

Near-IR metamaterials exhibiting dual-band negative-index behavior have been presented. Magnetic resonances in two bands are obtained by incorporating two resonators of different dimensions into one period of an infinitely periodic design. Negative permittivities are provided by thin silver films via the naturally available negative dielectric function at near-IR wavelengths. The desired bands of the NIM behavior can be designed by proper combinations of the magnetic resonator dimensions and the silver film thicknesses. A two-dimensional example with two negative-index bands in the near-IR spectrum was demonstrated. The two-dimensional design was then extended to a three-dimensional doubly-periodic dual-band metamaterial design. It has been pointed out that the use of silver strips or meshes in place of thin continuous films significantly improves the loss characteristics of the metamaterial.