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T型缝隙结构表面等离子波导的基本特性研究(英文) SurfacePlasmonWaveguidewithT-ShapedGrooves:FundamentalProperties Introduction Surfaceplasmonpolaritons(SPPs)havegainedincreasingattentionduetotheirpotentialapplicationsinnanophotonics,sensing,andsignalprocessing.OnewaytoconfineSPPsistousesurfaceplasmonwaveguides,whereSPPspropagatealongtheinterfacebetweenametalandadielectricmaterial.VariousstructureshavebeenproposedtoachieveefficientcouplingandpropagationofSPPs,suchasmetal-insulator-metal(MIM)waveguides,dielectric-loadedsurfaceplasmonpolariton(DLSPP)waveguides,andperiodicgratings. Inthispaper,wefocusonatypeofsurfaceplasmonwaveguidewithT-shapedgrooves(T-SPPwaveguide),whichwasproposedbyOzbayandcolleagues[1].TheT-SPPwaveguideconsistsofametalfilmwithaseriesofT-shapedgrooves,andadielectricoverlayer.SPPsareguidedinsidethegroovesandpropagatealongthemetal-dielectricinterface.Inthisstudy,weinvestigatethefundamentalpropertiesoftheT-SPPwaveguide,includingitsdispersionrelation,propagationlength,andmodeconfinement. DispersionRelation ThedispersionrelationoftheT-SPPwaveguidecanbederivedbysolvingtheMaxwellequationsandtheboundaryconditionsatthemetal-dielectricinterface.Theresultisatranscendentalequationthatgivesthecomplexwavevectorkasafunctionofthefrequencyω: k=k_r+ik_i wherek_ristherealpartofk,andk_iistheimaginarypart,whichdeterminestheattenuationoftheSPPs.ThedispersionrelationdependsonthegeometricalparametersoftheT-shapedgrooves,suchastheirwidth,depth,andperiodicity,aswellastherefractiveindexofthedielectricmaterial. Figure1showsthedispersioncurvesoftheT-SPPwaveguidefordifferentvaluesofthegroovewidthw.Aswincreases,theSPPmodeshiftstolowerfrequenciesandthepropagationlengthincreases.Foragivenw,thereisarangeoffrequencieswheretheSPPcanpropagate,knownasthesurfaceplasmonband.Thesurfaceplasmonbandnarrowsaswdecreases,becausetheconfinementinsidethegroovesbecomesweaker,andtheSPPscanleakintothedielectricmaterial. PropagationLength ThepropagationlengthLoftheSPPsintheT-SPPwaveguideisrelatedtotheattenuationcoefficientα,wh