It is known that the resonant length of a metallic dipole nanorod antenna is typically very much shorter than half a wavelength. Presence of a dielectric coating on the metallic core, intensifies this effect. The coating might be undesired (e.g. caused by metal corrosion) or desired (e.g. to protect metal from damage or corrosion). In this paper, an analytical method is presented to calculate the resonant (or effective) wavelength (λ_eff) of dielectric coated metallic nanorod antennas. Variation of λ_eff due to change in material properties and thicknesses is investigated. In order to validate the results, they are compared with those from full wave simulations approving the accuracy of the proposed method.

Keywords: Metallic nanorod, optical antenna, resonant wavelength.

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