Effect of radial anisotropy on plasmonic optical properties of coated nanorods

Plasmonic optical properties in pairs of coated nanorods in near-field are investigated by finite element method. The coated nanorod is composed of a radically anisotropic dielectric core and a metallic shell. Numerical simulations show that for a finite radial permittivity ¿_r, with the increase of the tangential permittivity ¿_t, the position of the near-field intensity peak shifts to long wavelength along with the decrease in the magnitude. On the other hand, with increasing ¿_r, the position of the intensity peak exhibits long-wavelength shift significantly, while keeping the maximal magnitude for isotropic case. Furthermore, a compensating effect for the decay of the intensity with the increase of the gap width can be achieved by manipulate the anisotropy of the dielectric core.