Nearly PML for an unconditionally-stable six-stages split-step FDTD method

A nearly perfectly matched layer (NPML) is developed for two-dimensional unconditionally-stable six-stages split-step finite-difference time-domain (FDTD) method. The algorithm is based on incorporating the split-step scheme and the Crank-Nicolson scheme into the nearly PML approach. In the proposed method, the Maxwell´s matrix is separated into six sub-matrices. Accordingly, the time step is divided into six sub-steps. Then, the formulation of the proposed method is derived. Furthermore, numerical results are carried out for different Courant-Friedrichs-Lewy numbers in two-dimensional domains, which shown that the method is validated numerically with FDTD-NPML.