Study On SPs And Application Of Composite Structure Of Dielectric Grating/metal Film With Silver Cube

As the central foundation in the research fields of surface plasmons?SPs?.optics,micro-and nanostructures arouse widespread attention of researchers.The composite dielectric grating/metal film structure possesses the advantages of simple operation,low cost,and shows promising application in exciting the SPs.Based on the composite dielectric grating/metal film structure,excitation of SPs and electric field enhancement are discussed by using the finite element method,furthermore,a composite dielectric grating/metal film with silver nanocubes structure is theoretically designed,the ultrahigh electric field enhancement generated by the resonant coupling of local surface plasmon and propagation surface plasmon in the composite structure is studied in this paper,on this basis,the application of the refractive index sensor with a composite structure based on dielectric grating/metal film is discussed.The specific research works and conclusions are as following:?1?A composite dielectric grating/metal film structure is theoretically designed,The material of the dielectric grating is SiO₂,Ag with thickness 45nm is selected as metal film.The SPs are excited by the laser with wavelength 442nm,by discussing the reflection spectra of the composite dielectric grating/metal film structure,the optimal parameters that allow the excitation of the propagation surface plasmon in the composite structure are selected,which is the grating period 312nm and thickness 90nm.The electric field intensity distribution and the electric field enhancement factor of hot spot in the composite structure is calculated,the electric field enhancement factor of hot spot is as high as2.54?10⁵.Furthermore,the composite dielectric grating/metal film structure is combined with the silver nanocubes,which exists in the position between the grating groove and the grating ridge.By discussing the extinction spectrum of the silver nanocubes,the optimal parameter of silver nanocube is70nm under the condition that the laser with wavelength 442nm is selected as exciting light.By discussing the electric field intensity distribution and the electric field enhancement factor in the composite structure,the hot spots of the composite structure mainly exists in the positions,which are the upper vertexes of silver nanocube in grating groove and the lower vertexes of silver nanocube in grating ridge.For the resonant coupling of local surface plasmon and propagation surface plasmon,the electric field enhancement factor of hot spot in the composite structure is as high as1.53?10⁶ under the condition of optimal parameters.?2?Based on the study of SPs in the composite dielectric grating/metal film structure and the composite dielectric grating/metal film with silver nanocubes structure,a refractive index sensor with a composite dielectric grating/metal film structure is designed.The surface plasmons are excited by the laser with wavelength 632.8nm,the refractive index sensor consists of SiO₂ substrate,SiO₂ dielectric grating filled with Si₃N₄,a Ag film with thickness45nm and the analytes.By the finite element method combining with wave vector matching equation and equivalent dielectric theory,the reflection spectras for the different grating thicknesses and periods are numerically simulated,a grating period of 500nm and a grating thickness of 100nm are selected as the optimal parameters.Under the condition of optimal parameters,the variation of the resonance angle of the interface between the metal film and the analyte with different refractive indexes is studied,and an angular sensitivity of 500?°?/RIU based on the refractive index sensor with a composite dielectric grating/metal film structure is obtained.