Complete optical transmission through nano-scale periodic metallic structure with three-stepped slits

Metallic structures with periodic array of subwavelength slits are well-known to lead to extraordinary optical transmission (EOT). Excellent power transmission originates from surface waves excited by incident transverse magnetic wave. Here we show that the metallic structure with array of three-stepped slits can transmit almost the entire power of incident wave into the substrate at desired optical frequency for low-temperature-grown gallium arsenide (LT-GaAs) substrate. Transmitted power of the proposed structure is studied both by an analytical model as well as numerical method by finite element (FEM). It is found that existence of three corners in the proposed structure can favorably confine generated carriers in the vicinity of the electrodes as this structure is used in photoconductive antenna (PCA); this feature contributes to increase terahertz (THz) current and subsequently THz radiation power of PCAs.