Dispersive Contour-Path FDTD Algorithm for the Drude–Lorentz Model

A dispersive contour-path algorithm is newly introduced into the finite-difference time-domain method for the analysis of arbitrarily shaped dispersive media expressed by the Drude-Lorentz (DL) model. The frequency-dependent formulation is performed using the simple trapezoidal recursive convolution technique. A faster convergence of the numerical results for an Au cylinder is found to be achieved over a wide wavelength range. In addition, the present method can suppress the spurious localization of surface plasmons caused by the conventional staircase approximation. The transmission characteristics of a grating consisting of a metal cylinder array are also revealed and discussed.