Extraordinary Transmission Through Ag-Si Structure Perforated With Rhombus Lattice Hole Arrays

This investigation elucidates the transmission characteristics of an Ag-Si structure on which an Ag film is perforated with a rhombus-shape of lattice holes. The transmission in the Ag-Si mode depends approximately linearly on the numbers of degenerate modes at long wavelengths at which the couplings between Ag-Si and Ag-air modes are weak. At the shorter wavelengths where Ag-Si and Ag-air modes are coupled together, the transmission intensities are approximately constant without an apparent peak at wavelengths longer than those of the Ag-air modes. The intensities decay rapidly at lower wavelengths owing the asymmetric slope of the Ag-air mode in the spectra.