Fano Resonances of Plasmonic Nanodisk

The Fano resonance of a single symmetry broken Ag nanodisk under a normal incidence was investigated by using finite-difference time-domain (FDTD) simulations. The asymmetry line shape of the Fano resonance was controlled by modifying the open angle of the nanodisk, and this Fano splitting was demonstrated as the result of the overlap between the broad dipolar and narrow quadrupolar modes, which could be strengthened by enlarging the radius of the nanodisk. A semi-analytical method was developed to calculate the plasmon hybridization, which was used to analyze the sub-process of the quadru Fano resonance. With the good agreement between theoretical calculations and FDTD simulations, the suggested method provides a way to investigate and control the Fano resonance inside a single planar nanostructure, and can be applied to the future high-performance Fano resonance sensors.