Tunablity of the unconventional Fano resonances in coated nanowires with radial anisotropy

Abstract

We establish full-wave electromagnetic scattering theory to study the near-field and far-field spectra of radially anisotropic coated nanowires. For coated nanowires containing radially anisotropic core and plasmonic shell, unconventional Fano resonances are predicted due to the interference between dipole cloaking mode and dipole resonant mode. In contrast to Z-shaped Fano profile with small modulation depth for coated nanospheres in Argyropoulos et al, Phys. Rev. Lett. 108, 263905 (2012), we predict S-shaped Fano profile with high depth for coated nanowires. An off-resonance field enhancement in the radially anisotropic core is found at the Fano dip, and its' magnitude is approximately the same as that the one at the low-energy resonant wavelength. Furthermore, with our adjustment of the inner size and the permittivity elements of the anisotropic core, tunable Fano-like profiles can be realized. These results may be useful for potential applications in different fields of nanotechnology.