Optical properties of single metal nanorods: An analytical model

TL;DR

This paper develops an analytical model for the optical properties of single metallic nanorods, accurately predicting resonance and scattering features, which aids in designing nanorod-based optical devices.

Contribution

An analytical model for metallic nanorods considering conduction currents and surface charges, providing explicit formulas for resonance and scattering properties.

Findings

Model agrees well with simulations

Derived formulas for resonance wavelength and dipole moment

Provides insights for nanorod optical design

Abstract

It is well known that the optical properties of spherical metal particles can be described with the Rayleigh approximation or rigorous Mie theory. But 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, extinction spectrum, and 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.