generation and manipulation of multiple magnetic fano resonances in split ring-perfect ring nanostructure

The plasmon resonances and field enhancement in split ring-perfect ring (sr-pr) nanostructure are investigated numerically by using a finite element method. multiple electric and magnetic fano resonances are achieved. the magnetic fano resonances are generated by the coupling between bright modes of the split ring (sr) and the dark modes of the perfect ring (pr). the wavelength as well as intensity of these resonances can be adjusted effectively by tuning the split angle of the sr, the gap distance between two rings, the width of two rings, and the offset of the pr along x-axis. calculation results exhibit that the maximum refractive index sensitivity exceeds 1225 nm/riu and the maximum figure of merit (fom) reaches 30.4. both electric and magnetic fields are greatly enhanced at the resonance peaks. this structure have potential application in sensor, multiwavelength surface enhanced spectroscopy, the propagation of low-loss magnetic plasmons, and advanced devices based on magnetic fano resonances.