Study On Multiple Fano Resonances Based On MIM Surface Plasmon Coupled Resonator

Surface plasmon polaritons（SPPs）is an electromagnetic wave pattern generated by the coupling of cluster oscillating free electrons on a metal Surface with external photons.SPPs have the ability to overcome light diffraction limit,especially based on SPPs metal-insulator-metal（MIM）waveguide structure with high constraints,low loss,long length of transmission and the advantages of the manufacture simple,therefore in high density integrated optical field has a very broad application prospects.Metal nanostructures,Fano resonance as a special form of resonance,the typical asymmetric sharp lines,can get higher detection sensitivity and figure of merit（FOM）,plus Fano resonance has the advantages of enhanced biological chemical sensing spectrum,so with the advantage of surface plasmons MIM waveguide combining,in the field of biological chemical sensing show a good application potential.In this paper,three Fano resonance sensing systems for MIM waveguide coupled resonator are designed based on SPPs theory.First,design the MIM waveguide coupling half ring cavity structure,research shows that when the incident wave transmission through the structure system of the two modes are produced when the Fano resonance,and can adjust the structure of geometric parameters and the refractive index of medium to flexible regulation of Fano resonance spectrum,calculate the FOM of the two mode can be as high as 3.05×10⁵ and 4.59×10^5,corresponding to the sensitivity of 800nm/RIU respectively and 1160 nm/RIU.Then,a structure of coupled semi-circular resonator containing silicon waveguide was proposed.When SPPs was transmitted in the structure system,three Fano resonances were formed.After parameter optimization,greater FOM and sensitivity were obtained,with values of 9.61×10⁵ and 1840 nm/RIU,respectively.Finally,due to the streamlined style widely popular in scientific research and industrial production,a MIM waveguide coupling streamlined resonant cavity structure is proposed,which can also generate triple Fano resonance.After optimization,better sensing performance was obtained,with the FOM up to 1.99×10⁶,and the sensitivity up to 2960 nm/RIU.The study shows that multiple Fano resonance can cause differential effect,which can effectively remove the influence of ambient temperature on refractive index when used as a refractive index device for detecting environmental medium.Therefore,the study of multiple Fano resonance has important application value in the field of biosensors.