Polarization dependent enhanced optical transmission through a sub-wavelength polygonal aperture surrounded by polygonal grooves.

Enhanced optical transmission (EOT) and its polarization extinction ratio (PER) of a sub-wavelength polygonal aperture surrounded by polygonal grooves are investigated numerically by finite difference time domain (FDTD) method. Effects of light polarization on EOT were analyzed and compared for four types of geometrical structures: triangle aperture surrounded by triangle grooves, square aperture surrounded by square grooves, rhombus aperture surrounded by rhombus grooves, and pentagon aperture surrounded by pentagon grooves. The effects of relative angles between the symmetry axes of polygons and the light polarization were thoroughly analyzed. Among these plasmonic polygonal bull's eye structures, the rhombus showed a maximum EOT several times larger than others. In contrast to the prior normal incident condition, we further analyzed the impacts of the incident angle and we found a wideband tunability of EOT wavelengths.