Demonstration of Negative Refraction in a Cutoff Parallel-Plate Waveguide Loaded With 2-D Square Lattice of Dielectric Resonators

A 2D negative-refractive index metamaterial is proposed and investigated, which is composed of a parallel-plate waveguide loaded with a square lattice of disc-type dielectric resonators. Collective and macroscopic behavior of the dielectric resonator lattice under the fundamental TE resonance gives negative effective permeability, whereas the parallel-plate waveguide below the cutoff for TE modes provides negative effective permittivity. Thus, the double-negative condition for the propagated waves with the appropriate polarizations can establish the left-handedness. Equivalent-circuit models are shown to give a good insight into the physical mechanism of the guided waves. Numerical simulation of the 2D dispersion diagram verifies the existence of the left-handed (LH) guided modes along with the isotropic characteristics. A triangular prism of the proposed LH structure that is sandwiched by the right-handed parallel-plate waveguides is designed and fabricated to directly observe the negative refractive index of the LH waveguide. The numerical and experimental results validate the negative refraction for the proposed structure.