Propagation Features of Metamaterial NRD Waveguides

Nonradiative dielectric (NRD) waveguides comprised of time-dispersive isotropic double-negative or single-negative slabs sandwiched between metal plates are studied. Dispersion features of bound (surface) modes are considered, showing how to achieve ranges of unimodal backward propagation by means of epsilon-negative media. Such ranges allow us to relax the symmetry constraints, typical of ordinary double-positive NRD guides, aimed at avoiding the excitation of the undesired LSE₀₁ dominant mode. Complex proper leaky modes supported by double-negative NRD guides are also illustrated, which show physical ranges of radiation into the first higher-order TE₁ mode of the background parallel-plate waveguide