Various mechanisms for efficient optical transmission through bilayered subwavelength patterned metal films

Light transmission through bilayered thin metal films perforated with subwavelength hole arrays are numerically studied based on a full-vector finite-difference time-domain approach. A variety of transmission peaks originating from different physical mechanisms are observed. In addition to the direct tunneling and Fabry-Pèrot resonances, generally possessed by idealized bilayered dielectric slabs, the near-field localized plasmon polaritons also play important roles. They not only influence the direct tunneling in a destructive or constructive way, but the interactions between these localized plasmon polaritons on both metal films also result in additional channels that transfer optical energy effectively.