Light transmission properties of double-overlapped annular apertures

We investigate the light transmission properties of double-overlapped annular apertures in a silver film with the three-dimensional finite-difference time-domain method. It has been found that the transmission peaks are attributed to the localized surface plasmon resonance (LSPR) of nanocavities and the surface plasmon polaritons (SPPs) of the nanoparticles. The peaks of the LSPR are blueshifted when the overlapping distance is increased. Moreover, a Fano-type resonance appears in the transmitted spectral response with an appropriate overlapping distance, which is elucidated as the hybridization results of the SPPs of the nanoparticles. The number and position of the Fano resonance can be tuned through varying the overlapping distance and other geometric parameters.