Multiple Fano resonances with flexible tunablity based on symmetry-breaking resonators

A symmetry-breaking nanostructure is proposed to achieve multiple Fano resonances. The nanostructure consists of an asymmetric ring resonator coupled to a plasmonic waveguide. The broken symmetry is introduced by deviating the centers of regular ring. New resonant modes those are not accessible to regular symmetric ring cavity are excited. Thus one asymmetric cavity can provide more than one resonant mode with the same mode order. As a result, the interval of Fano resonances is greatly reduced. By combining different rings with different asymmetric, multiple Fano resonances are generated. Those Fano resonances have different dependence on structural parameters due to their different physical origin. The resonance frequency and resonance peak number can be arbitrarily adjusted by changing the degree of asymmetry. This research may provide new opportunities to design on-chip optical devices with great tuning performance.