Low loss negative index metamaterials with one type of meta-atom

Metamaterial building blocks from microwave to optical range are mainly based on metal-dielectric composites. In almost all structures with true negative index (not coming from losses), two kinds of meta-atoms (electric and magnetic) are mixed to drive simultaneously the effective permittivity and permeability to negative values leading in turn to a negative index of refraction. In this paper, we show that two coupled structures with localized plasmons modes (e.g. cut-wires or split ring resonators) can exhibit negative refractive index by their own, by appropriately controlling the hybridization scheme of the plasmons modes. Because of small metal filling factor and reduced optical losses, the resulting structures may pave the way to realistic applications of metamaterials at optical frequencies.