Numerical investigation of the transmission enhancement through subwavelength hole array

The transmission characteristics of a metallic film with subwavelength periodic square hole arrays are investigated by using the three-dimensional finite-difference time-domain (3D-FDTD) method. The influences of the hole size, the refractive index of substrate, the refractive index of filled medium, the thickness of film as well as the incident angle on the characters of transmission spectra are studied. It is found that the transmission can be enhanced by filling the holes with higher refractive index medium. This enhancement can be explained by the collaboration of localized waveguide resonance with surface plasmon resonance.