A finite-difference time-domain method for Lorentz dispersive media with reduced errors within arbitrary frequency bands.

This work develops a finite-difference time-domain (FDTD) methodology with controllable accuracy within prescribed frequency bands, which is suitable for problems incorporating material dispersion described by the Lorentz model. An optimization technique is introduced, which is based on the one-dimensional (1D) numerical dispersion relation and modifies appropriately the form of the spatial operators. Through the implementation of a least-squares approach, the numerical wavenumber is forced to be close to the exact one within arbitrary parts of the frequency spectrum, located either below or above the medium's absorption band, according to the spectral content of the simulation. The formulation initially considers 1D problems and lossless materials. Yet, generalizations to multi-dimensional problems and the incorporation of at least low-loss materials are also discussed.