Strong enhancement of terahertz transmission for a three-layer heterostructure of metal hole arrays

The transmission characteristics of the three-layer metal hole array (MHA) are investigated in the subterahertz region. While the transmittance of the single-layer subwavelength MHA, the diameter of which is much smaller than the wavelength, is extremely low, the transmittance can be increased significantly by attaching the MHAs of the larger diameter on both sides of the subwavelength MHA. The finite-difference time-domain simulation is used to understand the mechanism of such a transmission enhancement phenomenon, and it is attributed to the enhancement of the electric field of the surface waves which are excited strongly on the surface of the outer-layer MHA.