Double Fano resonances in nanoring cavity dimers: The effect of plasmon hybridization between dark subradiant modes

Dark mode which is subradiant plays a key role in the generation of Fano effect. This study proposes that plasmon interaction between dark modes is a favorable method to generate multiple Fano resonances, where plasmon hybridization leads to the formation of a subradiant bonding and a subradiant antibonding combination. It demonstrates that a concentric ring/ring cavity dimer introduces interactions that render bonding quadrupolar ring mode dipole active, resulting in a pronounced Fano resonance. The corresponding antibonding quadrupolar ring mode is excited in a symmetry breaking nonconcentric cavity dimer, and double Fano resonances appear in the spectra.