Theory and experimental observation of hyperbolic media based on structural dispersions

Hyperbolic media usually possess large dissipation induced by the inherent imaginary part in the material dispersion of their metallic components. Here, we theoretically and experimentally demonstrate a route toward hyperbolic media with low dissipation: using structural dispersions. In a planar microwave waveguide filled with anisotropic dielectrics, we insert an array of metal wires and transform the original hybrid modes into pure transverse-electric modes. Interestingly, by engineering the structural dispersions such that waves are evanescent in one direction and propagating in the orthogonal direction, hyperbolic media with negligible loss can be achieved. Conical radiation pattern and negative refraction, which are characteristic phenomena of the hyperbolic media, have been numerically or experimentally demonstrated in microwaves. Our work opens an approach to utilize structural dispersions instead of material dispersions in realizing hyperbolic media with negligible loss.