FDTD Simulated Observation of a Gold Nanorod by Scanning Near-Field Optical Microscopy

Abstract

The optical properties of a gold nanorod were investigated by Imura et al. [J. Chem. Phys. 122, 154701 (2005)] using an apertured-type scanning near-field optical microscope (SNOM). The observed transmission image showed an oscillating pattern along the long axis of the nanorod. We obtain the image using the finite-difference time-domain (FDTD) method. Our model includes a nanorod on a glass substrate, a SNOM, and current as a light source. We develop a simple method for including the Drude-Lorentz dispersion relation of Vial et al. [Phys. Rev. B 71, 085416 (2005)] for gold in the FDTD. The oscillating pattern is explained by the total current in the nanorod, tip of the SNOM, and light source.