The collective property of enhanced transmission through compound metal periodic arrays of subwavelength apertures

The transmissions through a two-dimensional compound metal periodic hole arrays comprised of rectangle and cross-shaped holes are calculated by the finite-difference-time-domain (FDTD) method. The results show that the transmissions strongly depend on the collective effect of the compound hole cell. Moreover, the comparisons between transmission characteristics corresponding to the asymmetry of the cross-shaped hole in two different directions (vertical and parallel to the light polarization) are also studied. It is found that the 1168 nm peak is split into two peaks when the symmetry of the cross-shaped hole in y-axis direction is broken. However, it is shown that there is no obvious change of transmissions with changing the asymmetry in x-axis direction. Thus, it is concluded that the transmissions are more sensitive to the vertical direction asymmetry. The results may be utilized to tune the electromagnetic wave in subwavelength optics.