Diffractive coupling in gold nanoparticle arrays and the effect of disorder

Two-dimensional arrays of gold nanoparticles with a periodicity commensurate with the wavelength of resonant excitation of localized plasmons have been shown to exhibit a strong long-range interaction between particles. We investigate experimentally the effect of varying the degree of disorder in the geometrical arrangement from a periodic to a disordered lattice with constant occupancy. We also investigate the effect of disorder arising from variations in particle size for a regular lattice, and the effect this has on the broadening of the spectral line shape is discussed. A coupled dipole model is used to describe the observed spectral features.