Mu-Near-Zero Supercoupling

Here we theoretically predict and experimentally verify that permeability mu-near-zero (MNZ) materials give the opportunity to supercouple waveguides with highly mismatched cross sections. Rather distinct from the supercoupling provided by permittivity-near-zero materials we discovered several years ago, the MNZ supercoupling can take place when the transition channel cross section is much wider than that of the input and output waveguides. We develop a simple analytical model that captures the physical mechanisms that enable this remarkable effect. The MNZ supercoupling effect is experimentally verified with rectangular waveguide technology by mimicking the mu-near-zero response with the help of cylindrical split ring resonators.