Implementation of an efficient dielectric function into the finite difference time domain method for simulating the coupling between localized surface plasmons of nanostructures

An improved dielectric function was developed for the description of the dispersion of gold and silver in the wide spectral range between 180 nm and 2000 nm. The dielectric function can be used in the finite difference time domain method more efficiently and accurately than the four-Lorentzian terms (L4) model. We use it to study the effect of the interaction between the silica-core gold-shell nanocylinder pair on the localized surface plasmon resonance spectra (LSPR) and the simulation result shows that for a polarization direction parallel to the axis of the pair, the plasmon resonance wavelength increases when the width of the gap between nanocylinders decreases.