Surface plasmon polariton modes in coaxial metal-dielectric-metal waveguides

We explore the optical properties of a coaxial plasmonic metamaterial consisting of hollow dielectric cylinders with a diameter of 100-250 nm and a ring wall width of 10-50 nm, embedded in metal. We investigate the modal electric and magnetic fields and dispersion relation for different geometries and material choices of a single coaxial channel by using realistic values for all design parameters. The Fabry-Perot modes of a finite thickness slab are investigated with cathodoluminescence spectroscopy and explained by extracting the mode index from FDTD simulations. Furthermore, we investigate the coupling behavior of adjacent coaxes inside a hexagonal array. We find a change from the single-ring dispersion relation for coaxes with a ring-to-ring distance smaller than 20 nm.