Abstract
The effect of Siemens-star aperture geometry on terahertz transmission through the periodic subwavelength-sized hole arrays in a metal screen was investigated by finite-difference time-domain simulations and compared with experiments. Our modeling revealed that the extraordinary transmission frequency did not correlate with the array lattice constant as commonly believed, but was actually related to the aperture waveguide mode, the intensity and position of which depended strongly on the aperture geometry. By means of the aperture/array structure, the promising sub-micrometer terahertz band-pass width could be achieved by superimposing of such an aperture waveguide mode with hole array resonance and Wood's anomaly frequencies.