Nested structures approach for bulk 3D negative index materials

We investigate two generic conceptual ideas to obtain bulk 3D negative index metamaterials, which exhibit isotropic properties. One design is a traditional design of 3D wires ended with metallic plates. Another design is based on the nested structures approach, when one element providing magnetic response is inserted into another design with negative dielectric constant. Both constitutive elements possess cubic symmetry, thus we preserve it for the whole unit cell. The concepts can be applied for any frequencies; however, we are targeting optical and THz ranges. We report on numerical characterization of these particular designs finding negative index behaviour in ldquosplit-cube-in-cagerdquo and ldquosplit-cube-in-carcassrdquo designs. The latter design can be considered as reasonable candidate for isotropic bulk metamaterial showing good results in isotropy of effective properties and their fast convergence with the thickness of a sample.