Unsplit-field formulations for the higher-order PML

Based on the stretched coordinate perfectly matched layer (SC-PML) formulations and the auxiliary differential equation (ADE) method, an unsplit-field implementation of the higher-order PML scheme with more than one pole is proposed for truncating the finite-difference time-domain (FDTD) lattices. The higher-order PML has the advantages of both the conventional PML and the complex frequency shifted PML (CFS-PML). A numerical validation of the proposed formulations is given through a 2D TE-polarized electromagnetic wave interaction with an infinitely long perfectly electric conductor (PEC) sheet with the finite width. It is shown in the numerical simulation that the proposed PML formulations with the higher-order scheme are efficient in terms of attenuating both the low-frequency propagating waves and evanescent waves and reducing late-time reflections, and also hold much better absorbing performances than the conventional SC-PML and the convolutional PML (CPML) with the CFS scheme.