Research On Fano Resonance Effect And Its Sensing Characteristics In MIM Waveguide Coupled Resonator System

Surface plasmon polaritons(SPPs)are charge density waves propagation along the metal Surface,which are formed by interactions between incident photons and free electrons on metal surfaces.Due to its capability of overcoming the optical diffraction limit,it is possible to realize the propagation of light in the subwavelength scale.With the deepening of its research,photonic devices based on SPPs have been widely used in the fields such as light switch,filter,biochemical sensors and so on.Due to the advantages of small size,high sensitivity and easily integration,SPPs micro-nano sensors based on Metal-Insulator-Metal(MIM)waveguides have attracted much attention.Recent studies have shown that some novel nonlinear optical effects can be generated in MIM waveguide-coupled resonators,such as Fano resonance and electromagnetically induced transparency.Fano resonance is a weak coupling effect,which exhibits high sensitivity to the structure parameters and surrounding dielectric.Therefore,it is a very promising way to design high-sensitivity SPPs sensors by using the Fano resonance effect in MIM waveguide-coupled resonators.Based on coupled mode theory(CMT)and finite element method(FEM),the Fano resonance effect in MIM waveguide-coupled resonators is studied.Three kinds of high-sensitivity refractive index sensors based on Fano resonance effect are designed,the main work is listed as follows:1?The MIM waveguide coupled tooth and ring resonators structure is designed.The transmission properties and the refractive index sensitivity are simulated and analyzed with the FEM.The Fano resonance effect is observed in MIM waveguide-coupled resonators.The results showed that the sensitivity of the structure is 1057 nm/RIU and FOM value is 1016.Besides,two kinds of derivative structures are designed.Multiple Fano resonances are observed in the transmission spectra of the derived structures.The steady-state magnetic field distribution and the influence of structural parameters on the Fano resonance profile is alsostudied.2?The structure of MIM waveguide coupled with rectangular and ring resonators is designed.The transmission properties of the structure is investigated by the FEM.Simulation results show that an asymmetric Fano profile is observed in the transmission spectra,which result from the coupling between the narrow-band spectral response in the ring resonator and the broadband spectral response in the rectangular resonator.Based on the coupled mode theory,Fano resonance effect is analyzed.In addition,the refractive index sensitivity of the coupled structure is also studied and the highest value of sensitivity is 1125 nm/RIU.3?The structure of the defect MIM waveguide coupled with split ring resonator is designed.The simulation results showed that the transmission spectrum of the structure is obviously asymmetrical Fano profile.The profile can be easily tuned by changing the parameters of the structure.Besides,the sensitivity of the refractive index of the Fano resonance effect is also studied.The highest sensitivity value of the coupled structure is 1200nm/RIU.In this paper,three kinds of MIM waveguide-coupled resonators are designed.Light transmission properties of different structures is analyzed.The above works may provide some reference for the realization of Fano resonance effect in MIM waveguide-coupled resonators.