Influence of hole geometry and lattice constant on extraordinary optical transmission through subwavelength hole arrays in metal films.

We fabricate a series of square-lattice subwavelength circular, rectangular, and trapezoidal air-hole arrays drilled in opaque gold thin films and measured the transmission spectra of light passing through these metallic nanostructures in the near-infrared range. The measured results show strong dependence of extraordinary optical transmission on the lattice constant, hole size, and hole shape. The wavelengths of the transmission peaks and dips are mainly determined by the lattice constant. However, they are also influenced by the parameters of the hole size and hole shape. The experimental data agree well with numerical calculation results by means of a plane-wave transfer-matrix method when the detailed geometry of the air holes is fully considered. The results indicate that the extraordinary light transmission through subwavelength metallic nanostructures of air-hole arrays are governed by excitation of surface plasmon polaritons on the metal surface and their scattering by periodic air-hole arrays. [ABSTRACT FROM AUTHOR]