Splitting an asymmetric transmission peak by introducing magnetic-dipole oscillation on gold film

Asymmetric transmission (AT), the difference of transmission conversions, is closely related to the design of isolators, circulators, and polarization rotators. Tuning AT signal features, such as intensity and half-peak width at resonance peaks, is needed for polarization and direction sensitive beam splitters. In this paper, semicircular nanoholes are introduced into rectangular nanohole (RN) arrays and the AT effects of rectangular nanohole/semicircular nanohole (RNSN) arrays are investigated using finite-element methods. The semicircular nanohole induces magnetic-dipole oscillation around the rectangular nanohole, and this oscillation splits the AT peak of RN arrays. This feature is affected by the structural parameters of the RNSN. These results offer a novel method to split plasmonic resonant peaks for polarization and direction sensitive beam splitters.