Unconditionally Stable CN-PML Algorithm for Frequency-Dispersive Left-Handed Materials

An efficient and unconditionally stable stretched coordinate perfectly matched layer (PML) is proposed to truncate the computational domain of the finite-difference time-domain (FDTD) method, which is suitable to solve problems containing frequency-dispersive left-handed materials (LHMs). Here, the complex frequency-shifted scheme is used to combine the Crank-Nicolson Douglas-Gunn and auxiliary differential equation methods. A numerical example is carried out in the two-dimensional frequency-dispersive LHM domain, showing that the proposed PML is unconditionally stable for the time-step over the Courant-Friedrich-Lewy limit of the conventional FDTD.