A modified unsplit PML formulation for evanescent mode absorption in waveguides

In this letter, a modified unsplit perfectly matched layer (PML) formulation for the absorption of evanescent waves in waveguides is presented. The proposed formulation combines the advantages of the stretched coordinate and unsplit D - E - H PML formulations, which separates PML conductivities from the properties of the physical materials in the FDTD mesh. Results show that the proposed boundary outperforms the traditional unsplit PML in the evanescent region by 20 to 40 dB.