Investigation on the spectral properties of gratings based on FDTD method

Based on the Finite-Difference Time-Domain (FDTD) method, the perfectly matched layer (SAC-PML) absorbing boundary conditions (ABCs) combined with periodic boundary conditions (PBCs) were applied to the grating numerical model. Numerical calculations of spectral properties of the grating and smooth-surface structures were carried out. Absorptance of these two structures was obtained when the TM wave was used as the incident wave, and the metallic grating-coupled surface plasmon polarizations (SPPs) and the microcavity mode were discussed. The results indicate that, the absorptance of grating structure can be enhanced significantly compared with that of smooth-surface structure due to the present of SPPs and microcavity mode.