A Hybrid Sub-Gridding FDTD Method Analyzing Wave Propagation in Dispersive Metallic Gratings

A sub-gridding scheme that hybridizes the conventional finite-difference time-domain (FDTD) method and the unconditionally stable locally one-dimensional (LOD) FDTD method is proposed for the extraordinary optical transmission analysis of periodic metallic gratings. FDTD is applied to global coarse-grid regions while LOD-FDTD to local fine-grid regions. The dispersion of the metal, caused by evanescent waves propagating along the interface between the metal and dielectric materials in the visible and near infrared regions, is expressed by the Drude model and solved with a generalized auxiliary differential equation technique. A numerical example is provided to show accuracy and efficiency of the proposed method.