| Surface Plasmons(SPs)are electromagnetic waves formed by the interaction of photons and free electrons on the metal surface.It can break the traditional optical diffraction limit and has strong local field enhancement characteristics.It is divided into localized surface plasmons(LSPs)and surface plasmon polaritons(SPPs).Fano resonance is a quantum interference phenomenon,which is produced by the interference and coupling between a narrow discrete state(dark mode)and a wide continuous state(bright mode).Different from traditional symmetrical resonance,Fano resonance exhibits ultra-sharp and asymmetrical spectral line shape,with high refractive index sensitivity(S),high Figure of merit(FOM)and strong magnetic field enhancement.Due to these excellent characteristics,Fano resonance has potential applications in the field of optoelectronics,including highly integrated optical sensing technology,all-optical switches and filters.Although many Fano resonance structures have been proposed,the design of a new structure that can generate and regulate multiple Fano resonances is still a current research hotspot.This article is mainly divided into three parts for explanation:The first part mainly introduces the surface plasmons and three electromagnetic calculation simulation methods.This thesis uses the commercial software COMSOL Multiphysics 5.4 based on the finite element method for simulation,and mainly studies the multiple Fano resonance in the single-split ring and double-split disk nanostructure and the T-shaped cavity and split rectangular cavity MIM waveguide coupling system production and regulation.The second part mainly studies the surface plasmons resonance of Single-Split Ring and Double-Split Disk(SSR-DSD)nanostructures.When the incident light is perpendicular to the surface of the structure,the bright magnetic mode and the dark magnetic mode interfere with each other to produce magnetic Fano resonance.When the gaps of the double-split disk,cavity and single-split ring are synchronously shifted in the negative direction of the x-axis,high-order magnetic modes and double magnetic Fano resonance can be generated.On the basis of this structure,further adjusting the gap width of the single-split ring can enhance the intensity of the magnetic mode in the near-infrared region and generate triple magnetic Fano resonance;similarly,by adjusting the upper split angle of the double-split disk,In the visible light region,new high-order magnetic modes can be obtained,and triple magnetic Fano resonance can be generated.In addition,the maximum sensitivity and magnetic field enhancement of the structure reached 1400 nm/RIU and 69.7 times,respectively.These outstanding optical properties make the structure have potential application value in the fields of super-sensitive biosensors and multi-control magnetic Fano switches.The third part mainly proposes a plasma composed of metal-insulator-metal(MIM)waveguide,stub cavity(SC),T-shaped cavity(T-SC)and split rectangular cavity(S-RC)nanostructures,and use the finite element method(FEM)for numerical research.The results show that due to the interaction between cavity modes,triple Fano resonance appears in the transmission spectrum.The maximum sensitivity and maximum quality factor are 1600 nm/RIU and 14455,respectively.Changing the horizontal cavity and vertical cavity of T-SC can modulate the position and intensity of FR3,and modulating the height of S-RC makes transmission suppression stronger.New Fano resonance(NFR)can be generated by breaking the symmetry of the structure.In addition,by adding three semi-ring cavities and a semi-disk cavity to the original structure,we finally obtained eight ultra-sharp asymmetric Fano resonances.This design improves the integration and performance of the structure.Therefore,the device has potential application prospects in the field of refractive index sensors,optical communication and multi-control Fano switches. |
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