Marked effects of lateral displacement on the optical transmission properties of stacked artificial dielectric systems composed of metallic sub-wavelength slit arrays

Abstract

Metallic sub-wavelength slit-array slabs act just like dielectrics when the incident wavelength is longer than the slit interval. However, their stacked structures do not always exhibit optical properties equivalent to conventional dielectric multilayers, which should be due to the lateral periodicity. This work investigated in detail the lateral displacement dependence on the characteristics of the Fabry–Perot-like waveguide resonance modes of two-tier systems. Simulation studies clarified the behavior of the resonance modes and the physical mechanism underpinning the transmission disappearance by the lateral displacement. Furthermore, we determined that the critical frequency, above which the even-order modes exhibit blue-shifts with increases in the air gap spacing, can be predicted very accurately using a simple equation including the lateral displacement. Additionally, the transmission characteristics assessed experimentally were compared with the simulation results. The geometrically-tunable unique optical characteristics are expected to promote the future applications of artificial dielectrics operating in low-frequency optical regions.