Three-dimensional analysis of surface plasmon resonance modes on a gold nanorod

We investigate the surface optical properties of a gold (Au) nanorod by using the finite-element method in a three-dimensional model. Results from the near-field optical images show spatially oscillatory patterns (nodal fields) on the surface, and these are attributable to plasmon-mode wave functions. We interpret these phenomena in terms of the electric field nodes on the surface of the rod, and the results show good agreement with our experimental observation in the optical images.