Time-domain modeling of metal-dielectric nanostructures

We study second-order complex Padé approximants that give a systematic approach to time-domain modeling of dispersive dielectric functions including the classical Drude, Lorentz, Sellmeier and the critical points models. The approach is utilized to compare the frequency domain with time-domain simulations of local optical responses and transmission-reflection spectra for plasmonic nanostructures. Comparisons are made using auxiliary differential equations, recursive and piecewise linear recursive convolution formulations embedded in finite-difference, finite-volume, and finite-element time-domain solvers.