Optical properties of single metallic nanorods: An analytical model

Abstract

It is well known that the optical properties of spherical metal particles can be described with the Rayleigh approximation or the rigorous Mie theory. However, for the single metallic nanorods, a theory well capturing the fundamental resonance and scattering features is still absent. In this study, an analytical model is developed for the metallic nanorod, considering the longitudinally non-uniform conduction current and surface charges. With the circuit parameters deduced from the kinetic and electromagnetic energy of the nanorod, a formula, which agrees well with the simulations, has been suggested for the resonance wavelength of the fundamental longitudinal mode. Moreover, by introducing the radiative resistance to the circuit theory, the dipole moment, the extinction spectrum, and the near-field enhancement of the nanorod have been derived analytically and confirmed numerically. The results are important for understanding the optical properties of the metallic nanorods and provide a guideline for designing the light scattering and absorption.