Extinction spectra of silver nanoparticle arrays

The optical properties of silver nanoparticle arrays are studied by T-matrix and discrete dipole approximation (DDA) methods. Arrays of spherical silver particles with a radius of 30 nm are investigated with particular emphasis on the influence of array disorder on optical response. We find that the dipole peak intensities decrease when the array becomes disordered and the plasmon resonance wavelengths generally exhibit smaller blue shifts compared to perfectly ordered arrays. Using an extended DDA method, we calculate the extinction spectra of ordered nanodisk arrays, examining the variation of plasmon resonance wavelength with interparticle spacing (at fixed particle size). The calculated blue shift of the plasmon wavelength with decreasing interparticle spacing is found to be in excellent agreement with recent experiments.