Optical properties of square lattices of gold nanoparticles

We reanalyse optical measurements on two-dimensional lattices of ultrafine gold particles, produced by electron beam lithography. The spectra exhibit a distinct absorption peak due to the localized plasma resonance of the conduction electrons in the particles. The theoretical modeling used rigorous solutions, in the long-wavelength limit, for the polarizability of oblate spheroids and truncated spheres on a substrate. The dipole-dipole interactions between the particles in the square lattice were taken into account. We find good agreement between experimental and theoretical absorption peak positions for the case of oblate spheroids, but not for truncated spheres. Peak widths and minimum transmittances also show satisfactory agreement with theory.