lumerical plasmonics表面等离基元光子学器件仿真

FDTD2D/3DFDTD2D/3DPoissonandMODEWhy smonicsmonicsisafieldofstudythat the ctionoflightwavesandmetallic theresultingdensitywavesofelectronsthatcanbegeneratedfromthis Key UnderstandingandcalculatingthecomplexbehavioroflightinthepresenceofmetalnanostructuresSimulationgivestheopportunitytocheaplyandquicklytestideas,optimizedesignsandsolveproblems Expensiveandtime-consumingtobuild DesignoptimizationischallengingandresultsarenotalwaysSimulationSimulationComplexdeviceSimulationmethodologycanhighlydependentonthedeviceThiscanoftenleadtomistakesinthesimulationsetupandintheresultinterpretationFiniteDifferenceTime (FDTD)isastate-of-the-artmethodforsolvingMaxwell’sequationsincomplexgeometries Fewinherentapproximations= Averygeneraltechniquethatcandealwithmanytypesof Arbitrarilycomplex Onesimulationgivesbroadbandresults(comparetofrequencymethod,onceafrequency)Canbeusedtostudythe smoniceffectsofmicroandnanoscalemetalstructuresWhatdowewanttodosimulate?LocalfieldenhancementFarfielddistributionScattering/absorptionpropertiesTransmission/reflectionspectrumTotalortheamountintospecificregionsofthefarfieldOtherysisFluorescenceeffects,smonicwaveguideMetamaterials,efficiency smonicnano-Visualizerbullseye8smonic Design Material MeshSimulation Standalone Singledeviceona PeriodicOther smonic Metallic FluorescenceDesignParameterizetheUsethescriptedF.J.Garcia-Vidal,L.Martin-Moreno,H.J.Lezec,andW.Ebbesen,“Focusinglightwithasinglesubwavelengthapertureflankedbysurfacecorrugations,”Appl.Phys.Lett.83,4500(2003).DesignParameterizationcanincludepositionofsourcesandAnygroupcansetpropertiesoftheDesignEssentialLumerical’shierarchicalgrouplayoutandscriptbasedparameterizationmakesalmostanythingItisworththeinitialMeshWiththeFDTDmethod,itisnotpossibletoresolveinterfacestoahigherprecisionthanthesizeofthemeshused smonicsimulations,theresultsareoftenverysensitivetothesizeofthemeshnearinterfaces(skindepthissmall!).Use“meshoverrideregions”torefinethemesharoundsmallfeatures,curvedsurfacesthin ConformalmeshConformalmeshuniqueforFDTDConformalmeshtechnologyanintegralsolutiontoMaxwell’sequationsnearinterfacesLumerical’sapproachcanhandlearbitrarydispersive／lossymediaMoreadvancedthanwellknownapproachessuchastheYu-MittramodelforPEC

Yu-MittraapproachforConformalmeshThereare3variants variant0ConformalmeshappliedtoallmaterialsexceptmetalsandPECMetalsarematerialswith )<Thisisthesafest–YoumayneedtodosomeconvergencetestingwithotheroptionsifmetalsConformalvariantConformalmeshappliedtoallMaterialproperties–broadbandFiniteDifferenceTime (FDTD)simulationgivesbroadbandresult smonicdevicesusemetalmaterialsthatarestronglydispersiveatopticalfrequenciesWell-known =Userscandefinetheirownmodel,orimportfromexperimentaldata(realandimaginaryɛ(ω))FDTDisa technique:relationshipbetweenD&E D(t)=)*E(t)=E(tt-t 0Materialproperties–broadbandCommonsolutionsareLorentzorDrude OfteninsufficientforrealLumerical’sMulti-CoefficientModel(MCM)cansolveformaterialswitharbitrarydispersionsuchasAu,Ag,Al,Cu…etcmulticoefficientmaterial介电常数实 介电常数虚HowtogetCWresult?Resultscanbeinboth andfrequency分量E(t)和H(t)

E(w)=eiwtE(t)dt0 SimulationThesimulationmethodologycanbehighlydependentonthedeviceoperationandtheresultswewanttocollect.Inmostcases, smonicssimulationsfallinto1ofthefollowing3NoStandaloneWithsubstrate:(holesinmetals,ormetalislandsstandonnon-metalmaterials)SingledeviceonaPeriodicSimulationMethodologyforPeriodicDevicesPeriodicForperiodicWeoftenwanttostudytheresonanttransmission/reflectionpropertiesTotalorintoparticularPeriodicdevices:UserperiodicboundariesfortheperiodicThesimulationspanmustcorrespondto1unitcelloftheFordirectionswherethedeviceisuniform,useaspanof1meshUsesymmetrywhenpossibletoreducesimulationtimeandmemoryUserBlochboundariesforinjectionatnon-normalUsePML(absorbingboundaries)forthenon-periodic 8.0版及更高版本不再区分Periodicdevices:newavesshouldbeusedwithperiodicForinjectionatnon-normalUseBlochboundariesfortheperiodicForbroadbandsimulations,bewareofwavelengthdependenceofangleduetoguideForsteepangles,mnjectionrenjectionrePMLlayerswill erguideblochbroadbandPeriodicdevices:Usepowermonitorstogetthetotal Notethattransmissioninto–x/-y/-zdirectionwillbeMonitorabovedevice“T”measurestheMonitorbelowsource“R”measuresthe(negative)PeriodicForperiodicstructures,usethe‘gratingprojection’ratherthan‘farfieldprojection’functions:The“grating_transmission” ysisgroupcanbeusedtofindthetransmissionintoanyorderscriptsgratingPeriodic ceprofilemonitors anywhereinthenearfieldregiontostudythefieldprofile注意：记录的波长不要多，另外可以仅记录需要的量Usefarfieldprojectionstocalculateresultanywhere非FDTD ne cedinahomogeneousregioninthenear注意在Visualizer里面设置为周期（为方便，选5~10个周期即可,nottoo精确结果可以用Scriptnear

farSimulationMethodologyforStandaloneObjectsStandaloneForstandaloneWeoftenwanttocalculatetheabsorption/scatteringcrosssectionsEg.MIE

StandaloneUsePML(absorbingboundaries)onallPMLboundariesmustbeatleastahalfwavelengthawayfromanyscatteringstructure,sothatitdoesnotinctwiththeevanescentfieldsMeshUsemeshoverrideregionsandconformalmeshtorefinethemesharoundtheparticleStandaloneFDTDSolutionsprovidesaTotalField/ScatteredField(TFSF)source,whichisveryusefulforparticlescatteringsimulationsTFSFsourceisatype newavesourcethatseparatescomputationregionintotwodistinctTotalFieldregion-thesumof newaveplusthescatteredScatteredFieldregion-includesonlythescatteredField:是（复振幅）StandaloneWiththeTFSFsource,wecancalculatethepowerabsorbed/scatteredbytheparticleFDTDSolutionsprovidesa ysisthatreturnsthenetpowerflowoutofarectangularUseatrans_boxinside/outsideoftheTFSFsourcetocalculatetheabsorbed/scatteredpowerNotethatmonitorsmustnotoverlapwiththesourceinjectionregion( outsidemonitorboxreturnsthescattered

insidemonitorbox“total”returnsthe(negative)absorbedpower(becausewedefineoutgoingpoweraspositive)StandaloneThepowerreturnedbythetransmissionbox,“T”isthenetpowertransmittedout,andnormalizedbythesourcepower.Tocalculatetheabsorption/scatteringcrosssections,wewanttoinsteadnormalizebythesourceintensity(sourcepower/areaofsource):Pscat=T*sourcepower(f);#totalpowerinWFDTDSolutionsalsoprovides“cross_section” ysisgroupreturnsthecrosssectionsinthecorrectunits

outsidecrossysisgroupreturnsthecrosssection(SF散射场区

insidecross groupreturnstheabsorptioncrosssection（TF总场区，射场和散StandaloneAbsorption/ScatteringcrossStandalone Near ceprofilemonitorsanywhereinthenearfieldregiontostudythenearfieldenhancementFarCannotuseonlya nemonitorforthiscalculation,sincewehavetoconsiderlightscatteredintoalldirectionsThescat_ff ysisgroupcarriesoutthiscalculationbysummingupthecontributionsforallsidesoftheboxSimulationMethodologyforSingleDeviceonSubstrateSingledeviceonaForasingledeviceonaInsteadoflookingatthetotalscatteringcrosssection,wewanttostudyscatteringintospecificregionsinthefarfield“differentialscatteringcrosssection*”,ie.theintensityonasingleparticletothepowerscatteredbyitpersolidangleEg.Defectdetection/scattering, SingledeviceonaSimilartostandaloneobjects,usePMLonallPMLdistancemustbeatleasthalfwavelengthawayfromscatteringparticle,butlargerdistancemayberequireddependingonthetypeofsourceusedMeshUsemeshoverrideregionsandconformalmeshtorefinethemesharoundtheparticleSingledeviceonaUseTFSFsourcewhenthedeviceisuniformlyilluminatedbythesourceScatteredfieldsatsteepanglesrequirewidePleaserefer online:ApplicationsoftheTFSFSingledeviceonaUsenewavesourcewhenthedeviceisuniformlyilluminatedbythesource现在绝大多数散射均可以用PMLboundarieswilltruncatethe newave,leadingtodiffractionattheedgesofthesimulationareaSolution:runareferencesimulation(withthedeviceremoved).Oncetherealsimulationsiscomplete,subtractthefieldsfromthereferencesimulationstoleaveonlyfieldsduetodevicescatteringSingledeviceonaUseaGaussianbeamsource whenthesourcedoesnotuniformlyilluminatethedevicePMLboundariesmustbefarenoughawaytoavoidtruncatingtheUsescalarapproximationforGaussian/Cauchy/LorentziansourcesUsethinlenssource(vector)fortightlyfocusedspotsSingledeviceonasubstrate–DVDExample:in ctionofafocusedopticalbeam（NA薄透镜）andthestructured,goldsurfaceofatypicalDVDdiscCalculatethepowerthatwouldbecollectedbydetectorinthefarfield(withaspecifiednumericalaperture)ComparetheresultwithandwithoutthemetalposttodeterminetheoptimaldimensionsofthepostthatwillresultinastrongmodulatedsignalSingledeviceonasubstrate–parameterSweepthedimensionofthegold CalculatethepowerthatwouldbecollectedwithaNA=0.6objectiveinordertodeterminewhentheminimumsignalis

NA=Usefarfield2D/3DintegratefunctionstomeasurepowertransmittedintospecificregionsofthefarfieldSingledeviceonaUsefarfieldprojectionstostudytheangularneOthersmonicFDTDSolutions’IntegratedMODESolver,MODEModeprofiles,effectiveindex,propagationconstant,propagationloss,dispersion,bendingloss,groupvelocity,groupdispersionofsurfacesmonwaveguidesandmetal-insulator-metalCouplingefficiencybetweensurface smonwaveguidemodesandother nar,fiber)modesFarfieldradiationprofilesof smonwaveguideMetallic smonicFluorescenceNanoparticlescanbeusedtoenhancefluorescence（通常是两个或TwoIncreaselocalfieldofexcitationIncreasetheexcitationIncreasethedensityofradiativeIncreasethequantumefficiency(radiativedecayThetwoeffectscanbeassumedtobe

q:quantum =

gexc:excitation gexc

SeePalashBharadwajandLukasNovotny,"Spectraldependenceofsinglemoleculefluorescenceenhancement,"Opt.Express15,14266-14274(2007)Fluorescence

P

dipoleForanisotropicensembleoffluorophores,itcanshown

0

E= EWecanuseaMiescatteringsetupandrecord|E|2atthepositionofthefluorophoresFluorescenceDecayrateWecanrelatethedecayratetothedensityofstates(Fermi’sGoldenRule)WecanrelatetheclassicalEMpoweremittedbyadipoletotheimaginarypartofGreen’sfunction(GF)andthereforetothedensityofstatesResultisthatwecanrelatetheclassicalEMemittedtothedecayrate

=g0g

SeeL.NovotnyandB.Hecht,"PrinciplesofNano-Optics",CambridgeU