Study On The Controllable Fano Resonance Based On Coupled Square Ring Resonance Cavity

Plasmonics is an emerging science based on surface plasmon polaritons(SPPs).SPPs is a surface electromagnetic wave mixing mode strongly bounded to the metal-dielectric interface,which excited by the free electrons of metal interface and external photons.SPPs can overcome the diffraction limit,so that it can make the chip system easier to be integrated.Combined with the rapid development of nanotechnology,the plasmonic waveguides based on SPPs is particularly suitable for the design and fabrication of nanometer photonic devices in integrated optical circuit.Based on MIM-type surface plasmon waveguide,this paper present a new waveguide named Coupled Square Ring Resonance Cavity(CSRRC)waveguide structure.And a partial improvement is made to the waveguide structure so that other two waveguide structure can be presented,they are Coupled Square Split-Ring Resonance Cavity(CSSRRC)waveguide structure,Coupled Square Ring Resonance Cavity and Coupled Slot Resonance Cavity(CSRRC-CSRC)waveguide structure,respectively.The COMSOL simulation software based on finite element method(FEM)is used to simulate these three waveguide structure.The field distribution,Fano resonance and electromagnetic transmission characteristics of these three waveguide structure are studied in detail.Research indicates: CSRRC can produce single Fano resonance,and its transmission spectrum can be adjusted by changing the resonant cavity height H.Sensitivity and figure of merit(FOM)can reach 1180nm/RIU(Refractive Index Unit,RIU)and41099.1 ?,respectively.As an important parameter to measure the performance of nanometer optical switch,the extinction ratio can reach 40.85 dB.Therefore,CSRRC waveguide structure showing a good application prospects in nanometer optical switch design and application.By adjusting the location of the split on the CSSRRC,it can produce Fano resonance-Lorentz resonance and double Fano resonance.And its transmission spectrum can be adjusted by changing the resonant cavity length L and the width of split W.Sensitivity and FOM can reach 1700 nm/RIU and51031.1 ?,respectively.The Sensitivity and FOM of CSSRRC waveguide structure are better than many waveguide structure which have been studied.In view of this,CSSRRC waveguide structure showing a good application prospects in nanometer bio-sensor design.CSRRC-CSRC waveguide structure can produce double Fano resonance(Left Fano Resonance and Right Fano Resonance,LFR and RFR),LFR is generated by the interaction of the CSRRC with the waveguide.RFR is generated by the interaction of the CSRC with the waveguide.Hence,the double Fano resonance is only sensitive to the structural parameters of CSRRC and the parameters of CSRC,respectively.The LFR can be adjusted by changing the CSRRC height H,and RFR can be adjusted by changing the CSRC length L1.This characteristic provides a good application prospect for the waveguide structure in the design of nanometer optical splitter.