  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.
