Experimental verification of displacement-current conduits in metamaterials-inspired optical circuitry

Electric displacement current is present in capacitors and optical waveguides; however, unlike the conduction current in metallic wires, it is not confined. Analogous to the contrast in conductivity between a metallic wire and the surrounding air, displacement-current wires based on near-zero permittivity media contain a large contrast in effective permittivity. As a variation on this idea, in this Letter, we demonstrate at microwave frequencies two displacement-current cables based on effectively negative and effectively positive permittivity metastructures. Our experimental results clearly show cablelike behaviors that allow bending of the structure while still confining and maintaining the primarily longitudinal forward and reverse effective displacement currents within each conduit. The results presented here experimentally verify the notion of displacement-current wires and cables in metatronics as metamaterial-inspired circuitry.