Stability-Improved ADE-FDTD Implementation of Drude Dispersive Models

Graphene, which is considered to be a Drude dispersive model in the 0-10 THz frequency range, has recently received much attention due to its outstanding electrical and optical properties. This increases the interest in the auxiliary differential equation (ADE) implementation of Drude dispersion in the finite-difference time-domain (FDTD) algorithm. In this letter, detailed stability analysis of the ADE-FDTD scheme, which retains the second-order nature of Drude models, is investigated. It is shown that the stability of this scheme is more restrictive than the classical Courant-Friedrichs-Lewy constraint. To overcome this drawback, stability-improved implementation is presented. Numerical examples are included to verify these findings.