Theoretical analysis of extraordinary optical transmission through multi-lattices metal hole arrays in the terahertz region by coupled-mode method

Extraordinary optical transmission through multi-lattice metal hole arrays (MLMHA) in the terahertz region is investigated numerically by using coupled-mode analysis. MLMHA consist of two kinds of metal hole arrays (MHA) layer whose lattice constants are incommensurate with each other. By comparing the transmittance spectra of single lattice constant MHA and that of MLMHA, we observe the splitting and new peaks in the transmittance spectra for MLMHA. To study the origin of the new peaks, the transmittance spectra for MLHAL is compared with that of a system in which we filled the holes of MHA sandwiched between other MHA’s. We found that in the transmittance spectra for the filled holes MHA, only peaks associated with MHA sandwiched between other MHA’s vanish and the new peaks remained. Therefore, it is confirmed that the appearance of the new peaks is not due to the interaction between the surface modes of different lattice constant MHA’s. To clarify the mode pattern for split peaks we investigate the distributions of electric field outside MHA by rotating the MLMHA. The result reveals that the split peaks come out from the same peak mode. Consequently, it is found that the interaction does not occur between surface modes of different lattice constant MHAs.