Effective CNAD- and ADE-Based CFS-PML Formulations for Truncating the Dispersive FDTD Domains

An effective and unsplit-field implementation of the complex frequency-shifted perfectly matched layer (CFS-PML) based on the Crank-Nicolson-approximate-decoupling (CNAD) and the auxiliary differential equation (ADE) method is proposed to truncate the dispersive finite-difference time-domain (FDTD) domains. The proposed formulations take full advantage of the capacity of the CFS-PML for attenuating evanescent waves and reducing late-time reflections. Furthermore, the proposed formulations have an advantage of the unconditional stability of the original CN-FDTD method. Two numerical tests have been carried out to validate the proposed formulations in the two-dimensional FDTD domains composed of the linear Debye and the Lorentz dispersive media, respectively. It is shown in the numerical tests that the proposed formulations can not only increase the time step size over the Courant-Friedrichs-Lewy (CFL) limit as compared with the conventional FDTD, but also hold good absorbing performance.