Three-Dimensional Anisotropic Zero-Index Lenses

We propose, design, and experimentally demonstrate three-dimensional 3-D anisotropic zero-index lenses, which can improve the directivity of traditional antennas. We show that a 3-D anisotropic zero-index lens with εu → 0 is efficient to transverse magnetic (TM) modes and can decrease the beam width of the main lobe in the E-plane; while a 3-D anisotropic zero-index lens with μu → 0 is efficient to transverse electric (TE) modes and can reduce the beam width of the main lobe in the H-plane, in which u represents the propagating direction. If such two lenses are packed together, the directivity of both E- and H-planes is significantly improved. To verify this unique property, we design and fabricate four 3-D anisotropic zero-index lenses using metamaterials in the microwave frequency and perform the experiments in the anechoic chamber. Experimental results demonstrate that the beam widths of both E- and H-plane gain patterns are greatly reduced, which have good agreements to the full-wave simulations.