Multipolar Fano Resonances and Fano-Assisted Optical Activity in Silver Nanorice Heterodimers

We propose a simple structure of a silver nanorice heterodimer to achieve both Fano resonances and strong optical activity. Due to the ellipsoid shape of nanorice, the dimer shows a unique plasmon hybridization picture, being different from those in previously studied two-nanoparticle coupling, which benefits the generation of Fano resonances here. Under oblique incidence, this nanorice dimer exhibits not only multipolar Fano resonances but also very strong optical activity in the Fano resonant ranges. A chiral molecule model is proposed to explain the generation of chirality. It is also shown that Fano resonance has an assisting effect on optical activity (especially for subradiant modes), which can be ascribed to the energy transfer from the super-radiant modes to the subradiant modes during Fano interference.