A Broadband Three-Dimensionally Isotropic Negative-Refractive-Index Medium

When designing negative-refractive-index (NRI) metamaterials, scientists have struggled to overcome three primary obstacles: polarization dependence, narrow bandwidth, and fabrication challenges. Here, we address these issues with the design of a three-dimensional, fully isotropic, broadband NRI medium that can be produced on a large scale. The simulated structure exhibits a NRI bandwidth of 24.1%, more than twice that achievable using a typical split-ring resonator/wire medium. A four-hundred-unit-cell slab measuring 15 cm x 15 cm x 6 cm is fabricated and used as a flat NRI lens. The lens produces a super-resolved focus independent of the type of source or its polarization.