Surface plasmon polariton and mode transformation in a nanoscale lossy metallic cylindrical cable

A theoretical investigation on the surface plasmon polariton in a gold cylindrical nanocable is presented. By solving a complete set of Maxwell's equations in the nanocable (with a 50 nm radius gold nanocore, 10--300 nm silica layer, and 30--200 nm gold nanocladding), the dispersion relations on the optical frequency and on the silica thickness are discussed. When the silica thickness varies from 50 to 250 nm, at a fixed wavelength, the strong coupling between the gold nanocore and the nanocladding leads to a symmetric-like surface mode and an antisymmetric-like surface mode in the nanocable. The transformation between the surface mode and the waveguide mode in this structure is also investigated. The results will be helpful for understanding the surface waves in the subwavelength structures.