The effect of nanorod position on the plasmonic properties of the complex nanorod in nanohole arrays

Abstract

By moving the nanorod (NR) from the middle toward the rim of the nanohole (NH), i.e. breaking the geometric symmetry, the extraordinary optical transmission (EOT) caused by the dipole coupling of the localized surface plasmon resonance of the NR and the NH can be tuned to redshift exponentially while maintaining the high transmission and overall dimension of the structural unit. This resonant wavelength shift depends strongly on the moving direction of the NR, i.e. whether it is along the long axis or short axis of the rod. Connecting the NR to the NH and increasing the lattice period can significantly redshift the EOT mode, allowing ultra-high transmission in the mid-infrared (MIR) region. The high local E-fields, enhanced propagating waves with a tunable visible-MIR resonance wavelength, make this structure suitable for the design of compact and integrated optical devices from the visible to the MIR wavelength range. In addition, Fano resonances are emerging due to the coupling and hybridization of different plasmonic modes, making the structure beneficial for high sensitivity measurement.