A finite difference time domain model for scattering by dispersive media

A Finite Difference Time Domain (FDTD) method for Scattering of electro-magnetic pulses by dispersive dielectric objects IS developed. Two models for dispersive polarizable materials are examined. One has a complex susceptibility with a single pole in the complex frequency plane; the other is a standard model based on atomic oscillators with damping, which allows for multiple poles in the complex susceptibility. Theoretical and computer algorithms for FDTD calculation for both models were developed, including appropriate absorbing boundary conditions near the boundaries of the spatial grid used. Numerical calculations were done for a linearly polarized plane wave pulse of short duration incident from vacuum on a semi-infinite dispersive slab and on a dispersive sphere. The results were compared to appropriately superposed frequency domain solutions in order to demonstrate the accuracy and utility of this new FDTD algorithm.