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27606_ftp.pdf

27606_ftp.pdf

上传者: 用户7f7nzqj0vk 2014-04-01 评分 0 0 0 0 0 0 暂无简介 简介 举报

简介:本文档为《27606_ftppdf》,可适用于IT/计算机领域,主题内容包含JDBaena,JBonache,FMartin,RMarques,FFalcone,TLopetegi,MAGLaso,JGarcia,IGil,符等。

JDBaena,JBonache,FMartin,RMarques,FFalcone,TLopetegi,MAGLaso,JGarcia,IGil,andMSorolla,Equivalentcircuitmodelsforsplitringresonatorsandcomplementarysplitringresonatorscoupledtoplanartransmissionlines,IEEETransMicrowaveTheorTech(),–XCheng,etalCharacterizationofmicrostrippatchantennasonmetamaterialsubstratesloadedwithcomplementarysplitringresonators,MicrowaveOptTechnolLett(),–Dong,HToyao,andTItoh,Designandcharacterizationofminiaturizedpatchantennaloadedwithcomplementarysplitringresonators,IEEETransAntennasPropag(),–MManteghiandYRahmatSamii,Multiportcharacteristicsofawidebandcavitybackedannularpatchantennaformultipolarizationoperations,IEEETransAntennasPropag(),–PHallbjorner,ThesignificanceofradiationefficiencieswhenusingSparameterstocalculatethereceivedsignalcorrelationfromtwoantennas,IEEEAntennasWirelPropagLett(),–VCWileyPeriodicals,IncLOWPOWERPHOTONICCONTROLOFAMICROWAVERINGRESONATORUSINGBULKILLUMINATIONMohammadAliShiraziHosseinidokhtandManiHosseinZadehCenterforHighTechnologyMaterials,Goddard,SE,Albuquerque,NMCorrespondingauthor:mhzchtmunmeduReceivedOctoberABSTRACT:WedemonstratethefeasibilityofbulkilluminationtechniqueforlowpowerphotoniccontrolofRFresonanceUsingthistechnique,thetransmittedRFpowerthroughamicrostriplineringfilteronajunctionlesssiliconsubstrateischangedbydBwithlessthanmWofinteractingopticalpowerVCWileyPeriodicals,IncMicrowaveOptTechnolLett:–,ViewthisarticleonlineatwileyonlinelibrarycomDOImopKeywords:lightcontrolledRFdevicesRFringresonatorRFphotonicsINTRODUCTIONPhotoniccontrolofRFsignalpropagationisanimportanttopicthatcontinuestobeanactiveareaofresearchanddevelopmentinmicrowavephotonics–PhotoniccontrolhasmanyadvantagesoverconventionalelectricalcontrolHighdegreeofelectricalisolationbetweenthecontrolsignalandthemicrowavecircuit,immunitytoparasiticelectromagneticradiation,highpowerhandling,overallweightreduction,highspeedcontrol,andtimingprecisionareamongthemostimportantbenefitsofphotoniccontrolInparticular,electricalisolationbetweenthecontrolsignalandthemicrowavestructureiscrucialfordesignandfabricationofreconfigurableantennas–wheretheradiationpatternandefficiencyareaffectedbythepresenceofcontroldevicesandcircuitsinthevicinityofantennapatternAlargevarietyoftechniques,devices,andmaterialshavebeenexploredfordesigningphotonicallycontrolledswitches,phaseshifters,andattenuatorsInalmostalltheseapproaches,photoniccarriergenerationinasemiconductorcontrolstheamplitudeandthephaseoftheRFsignalpropagatingonmicrostriporcoplanartransmissionlinesFreecarriergenerationinbiasedandunbiasedjunctionsaswellasjunctionlessregionshavebeenusedtocontroltheRFfieldindiscontinuities,,stubs,,resonators,andterminations,,ExceptfewcaseswherethephotosensitiveelementisaddedtoatransmissionlinefabricatedonalowlossRFsubstrate,,,inmostproposedstructurestheRFcircuitisfabricatedonthephotosensitivesemiconductorsubstrateinordertoreducethecomplexityofthefabricationprocessandkeepthedevicemonolithicAlthoughcompoundsemiconductorshavealsobeenusedasthestructuralmaterialsinthesedevices,,implementationofphotonicallycontrolledRFdevicesonsiliconsubstratesismoreattractiveformonolithicintegrationofmicrowaveandmmwavedevicesusingwelldevelopedfabricationprocessesIndependentofthematerialandthedevicestructure,inalltheseapproachesanddevicesalaserwavelengthbetweenandnmisusedtomaximizeopticalabsorptionandcarriergenerationAsaresult,theopticallyaffectedregionhasbeenconfinedatthesurface(duetosmallopticalpenetrationdepthatthesewavelengths)Incontrasttothepreviouswork,hereweexplorethepotentialapplicationofbulkilluminationatalongerwavelength(nm)combinedwithhighQRFresonancetomaximizetheRFopticalfieldoverlapMoreover,weuseasidecoupledRFringresonatortoconfinetheRFfieldandenhancetheinteractionofRFfieldandphotogeneratedcarriersNotethatalthoughpreviouslycertainplanarresonantstructureswereusedforphotonicRFcontrol,theconfinementoffreecarrieronthesurfacehaslimitedtheinteractionoftheresonantfieldandthefreecarriersInthesecases,thepresenceoffreecarriershasbeenmainlymodifyingtheelectricalpropertiesattheboundariesoftheresonator(effectivelytailoringtheconductorsize)ThisarticledescribesaphotonicallycontrolledRFringresonatorsuitableforcontrollingavarietyofsiliconbasedmicrowaveintegratedcircuitsByopticallycontrollingthedensityoffreecarriersintheregionsofthesubstratewithlargeresonantRFfield,wehavedemonstrateduptodBoftransmissionlossvariationwithonlymWofinteractingopticalpowerfromacommercialfiberpigtailedlaserdiodeoperatingatnmToourknowledge,thisisthelargestopticalsensitivityofRFtransmissioneverreportedforapassivejunctionlessphotonicallycontrolledmicrowavedevicePHOTONICALLYCONTROLLEDRFRINGRESONATORBulkVersusSurfaceIlluminationAsphotonicfreecarriergenerationcontrolstheRFpropagationinmostopticallycontrolledcomponents,strongopticalabsorptionisthemaincriteriaforchoosingthephotoconductivematerialandthecorrespondingwavelengthOntheotherhandtoreducethefabricationcostandcomplexity,preferablyonlyonetypeofmaterialisusedinthedevicestructureAsaresult,lowlossopticalwaveguidescannotbeeasilyintegratedwiththedevicetodeliverlightdirectlytothesensitiveregion,andalmostalldevicesarecontrolledbytopilluminationtoavoidabsorptionbeforereachingthesensitiveregionSiliconisoneofthemostcommonsubstratesusedinphonicallycontrolledRFdevices(mainlybecauseofcompatibilitywithICfabricationandlowfabricationcost)Figure(a)showstheabsorptiondepth(d,thedepthatwhichthelightintensitydropstoofitsvalueattheinterface)plottedagainstwavelengthforsiliconsubstrateBelowlm,dislessthanlm,andallthephotogeneratedcarriersareeffectivelyconfinedatthesurface(interfacebetweenairandsilicon)ThatiswhysofartheopticalcontrolhasbeenmainlyachievedbytailoringtheconductivestructureontopofthesemiconductorsubstrateusinglaserbeamHere,weexamineanalternativeapproachbychoosingawavelengthwithanabsorptiondepthlargerthanthesubstrateMICROWAVEANDOPTICALTECHNOLOGYLETTERSVol,No,JulyDOImopthicknesstoenablebulkillumination(photogeneration)and,therefore,enhancedinteractionbetweentheRFfieldandthephotogeneratedcarriersInaddition,weuseanRFringresonatorthatconfinesandpassivelyamplifiestheRFfieldinarelativelysmallregionBulkilluminationofthevolumewithmaximumelectricfieldintensityresultsinalargeRFoptical(and,therefore,RFfreecarrier)overlapintegralInourexperiment,weusethenmwavelengthwithanabsorptiondepthofaboutmmthatistwotimesthethicknessofthesubstrateSothephotocarriersaregeneratedalmostuniformlydistributedacrossthewaferExperimentalSetupThestructureconsistsofRFringresonatorsidecoupledtoamicrostriplineRFringresonatorhasbeenextensivelyinvestigatedinthecontextofplanarantennasandfrequencyselectivesurfaces–Theringresonatorandthetransmissionlinearefabricatedonalmsiliconsubstrate(orientation)witharesistivityofaboutXcmAthinlayer(lm)ofcopperwascoatedonbothsidesofthesiliconwaferusingRFsputtering(nmofchromiumwasusedbetweencopperandsilicontoimprovetheattachment)Next,wepatternedthetopcopperlayerusingphotolithographyandwetetchingFigure(b)showstheringresonatorsidecoupledtothemicrostriplineTheringresonatorhasadiameterofmmandawidthofmmThemicrostriplineisaXline(widthmm),andtwoSMAlauncherswereusedtocoupleRFpowerintoandoutofthemicrostriplineFig(b)Whenaringresonatorissidecoupledtomicrostripline,thedegeneracybetweenfrequenciesoftheevenandoddresonantmodeswillberemovedbecauseoftheasymmetriccoupling,Asaresult,twodipsappearneareachresonanceinthetransmissionspectrumofthemicrostriplineWehaveusedafiniteelementmicrowavemodelingsoftware(CST)tocalculatethefrequenciesandthefielddistributionforthefirsttwomodesoftheringresonatorFigureshowsthesimulatedtransmissionspectrum(S)aswellastheelectricfielddistributionforthefundamentalandthesecondharmonicmodeoftheringresonatorBelowGHz,fourmodesareexcited:theoddfundamentalmode(Mo),evenfundamentalmode(Me),oddsecondharmonicmode(Mo),andevensecondharmonicmode(Me)Usingthesimulationresults,wehaveidentifiedthreedifferentlocationscorrespondingtotheminimumfieldstrengthforeachoneoftheRFmodesforopticalilluminationseeFig(a)AsmallcircularapertureonthecopperringisusedtoexposethesubstratetolaserateachoneoftheselocationsThediameterofapertureismm(aboutoftheringwidth)tominimizeitseffectontheRFresonanceFig(b)Wefabricatedthreesampleswithidenticalringsandcouplinggapsbutwithdifferentaperturepositions(soeachringhasonlyoneaperture)AsshowninFigure(c),thenmlaserlightfromafiberpigtailedlaserdiodeisfedtoafiberpigtailedcollimatorandisverticallycoupledtothesubstratethroughtheapertureFigure(a)Absorptiondepthofthesiliconplottedagainstwavelength(b)AphotographoftheringcoupledtoamicrostriplineonasiliconsubstrateColorfigurecanbeviewedintheonlineissue,whichisavailableatwileyonlinelibrarycomFigureSimulatedtransmissionspectrumofthemicrostriplinecoupledtotheringresonator(a)Nearthefundamentalresonance(b)NearthesecondharmonicresonanceThearrowsshowtheeven(fe)andodd(fo)modesforeachresonanceTheinsetsshowtheelectricfieldmagnitudeonaplanelocatedinthemiddleofthesiliconsubstrate(lmdepth)Colorfigurecanbeviewedintheonlineissue,whichisavailableatwileyonlinelibrarycomDOImopMICROWAVEANDOPTICALTECHNOLOGYLETTERSVol,No,JulyFigure(a)ThelaserisilluminatingLocation(theminimumfieldintensityforevensecondharmonicmode)(b)ThelaserisilluminatingPosition(theminimumfieldintensityforevenfundamentalmode)(c)ThelaserisilluminatingPosition(theminimumfieldintensityforoddfundamentalmode)Figure(a)Thelocationoftheapertureonthreedifferentringresonators(b)CloseupphotographofaringwithanapertureatPosition(c)SchematicdiagramofthecollimatorverticallycouplinglaserlighttothesiliconsubstrateColorfigurecanbeviewedintheonlineissue,whichisavailableatwileyonlinelibrarycomMICROWAVEANDOPTICALTECHNOLOGYLETTERSVol,No,JulyDOImopMeasurementandResultsFigureshowstheSmeasurementresultsnearfundamentalandsecondharmonicresonanceintheabsenceofthelaserilluminationandwiththreedifferentlevelsofincidentopticalpower(,,andmW)TheincidentopticalpowersareestimatedbasedontheopticaloutputpowerfromthecollimatorandtheapertureareaTheresonantfrequenciesoftheoddandevenfundamentalmodesaswellastheevensecondharmonicmodesareingoodagreementwithvaluedfromtheSmeasurementAccordingtothesimulation,theMoisweaklycoupledtothemicrostripline(SdB)andthatiswhyitishiddenintheparasiticbackgroundtransmissioninthemeasuredspectrumInFigure(a),thelaserisilluminatingLocationwheretheEfieldintensityfortheMeisminimum(accordingtosimulation)AsthislocationisnearthemaximumoftheMe,thismodeissuppressedbyphotocarriergeneratedlossTheresonantdipoftheMoandtheMearealsoreducedthisisduetothreemainreasons:theresonantelectricfieldofthesemodesisnotcompletelyzeronearintheilluminationregion,thereallocationoftheminimumfieldintensitymightbeslightlydifferentfromthesimulation,andsomecarrierswilldiffusetohighfieldregionInFigure(b),thelaserisilluminatingLocationwhereelectricfieldintensityforMeisminimumAsexpected,theMeisminimallyaffected,whereasMoiseffectivelydisappearedandMeisseverelyattenuated(PositionhasasignificantoverlapwiththefieldintensityofMe)InFigure(c),thelaserisilluminatingPositionwherethemaximumofMeislocatedInthiscase,weobservethemaximumattenuationforMemodeTheseresultsshowthatusingbulkilluminationonecanselectivelycontrolthelossfactorofdifferentmodesDuetotheabsenceoftheMo,nearGHztheilluminationonlycontrolsthemagnitudeoftheevensecondharmonicwithminimalfrequencyshiftSoeffectivelynearthesecondharmonicresonance,thedevicefunctionsasasinglefrequencyopticalRFswitchFigureshowstheRFqualityfactor(unloaded),frequencyandthetransmittedRFpower(S)atfRFf,e,MHz(resonantfrequencyofMe)plottedagainsttheinteractingopticalpowerNotethatatasinglewavelength(nm),opticalreflectionfromthesilicon–airinterfacecanbeeasilycanceledbydepositingtwolayersofdielectricontopofthesiliconwithalmostnoeffectontheRFpropertiesTherefore,toestimatetheultimateperformanceofthedevice,herewehaveconsideredtheopticalpowerinsidethesilicon(ortheinteractingopticalpower)insteadoftheincidentopticalpowerTheunloadedRFqualityfactorineachcasehasbeenestimatedusingtheSspectrumbasedonthedBlinewidthmeasuredfromthebottomofeachtransmissiondipAsexpected,thequalityfactorofthemodesdegradesduetolossgeneratedbyfreecarriersThefrequencydoesnotchangewhenaperturenumberstwoandthreeareilluminated,anditchangesonlybywhenaperturenumberoneisilluminatedNotethatinalmostallresonantcasesstudiedpreviously–,theopticallyinducedattenuationisaccompaniedwithsignificantfrequencyshiftHere,thefrequencychangeisminimal,becausethephotocarriersdonotincreasetheRFlengthasopposedtopreviousresonantstructureswherethephotogeneratedcarriersatthesurfacechangetheconductingsurface(thereforetheresonatorsize)andtheresonantfrequencyDecouplingthefrequencyshiftandattenuationisveryimportant,becauseinnarrowbandFigureMeasuredvaluesofRFqualityfactor(a),resonantfrequency(b),andSatresonance(c)plottedagainstopticalpowerinthesubstrate(interactingopticalpower)TheseparametersareonlymeasuredforMe(f,e,MHz)andV–VcorrespondtoilluminationatPositions–Colorfigurecanbeviewedintheonlineissue,whichisavailableatwileyonlinelibrarycomTABLEComparisonBetweenthePerformanceoftheProposedDevicesandPreviouslyShownOpticallyControlledRFDevicesReferenceWavelength(nm)dB(Wmm)dBmWGeometryFrequency(GHz)MaterialThisworkRingSiliconXStubSiliconXStubSiliconXXOVCIII–VXInterdigitalSiliconXCPWgapSiliconXearclampXWaveguideSiliconXStubSiliconXSigapSilicon<XStubSiliconXCPWgapSiliconDOImopMICROWAVEANDOPTICALTECHNOLOGYLETTERSVol,No,Julyresonantsystems(suchasfilters)attenuationatcertainfrequenciesisdesiredTablesummarizesthesomeoftheresultsfrompreviousworksonphotonicallycontrolledRFcircuitsIndependentofthematerialandthespecificdesign,alldevicesuseopticalilluminationtocontroltheRFfieldthroughphotocarriergenerationClearlyintermsofmaximumRFtransmissionchangepermWofopticalpower,ourdeviceoutperformsthepreviousdevicesAllthesedevicesfunctionbasedonopticalsurfaceeffects(k<lm)andsomeofthemusecomplexstructures,junctions(biasedandunbiased),andcompoundsemiconductormaterialThedevicepresentedinthisworkiscompletelymadeonauniformsiliconsubstrateanddoesnotuseanybiasvoltageorp–njunction,yetithasthelargestopticalsensitivityTheenhancedsensitivityisaresultoflargeoverlapbetweenthephotocarrierdensityandtheoscillatingRFfieldinthesiliconsubstrateDISCUSSIONThedevicepresentedherehasmanyapplicationsinopticalswitchingofmicrowavepowerandthedesignofopticallyreconfigurableRFcircuitsandantennasThesamestructurecanalsofunctionathigherfrequenciesbyreducingtheringresonatordiameterorusinghigherharmonicsofthesameringWeexpectbetteropticalsensitivityinsmallerringsduetothelargerratiobetweentheopticallyattenuatedRFfieldandthetotalresonantRFfiledMoreover,bycouplingmorerings,severalfrequenciescanbeswitchedsimultaneouslyresultinginmoreflexibleandversatileRFtransmissionspectrumDuetolowpowerconsumption,onelasercanfeedseveralresonatorsusinglowcostpowersplittersandcollimatorsFigure(a)showsthreeidenticalcoupledringresonatorscomprisingathreepoleRFbandstopfilter(threestopbandsshowninthefigure)Asshown(graytrace),laserilluminationofallthreeringscaneliminatethesecondstopbandwithoutsignificantlychangingtheotherstopbandsByproperlyilluminatingdifferentlocationsoneachring,onecantailorthetransmissionspectrumofthefilterwithoutanyphysicalcontactorusinganyelectronicmechanicalelementFigure(b)showsadesignwhereringresonatorswithdifferentdiametersaresidecoupledtoasingletransmissionlineInthiscase,aseriesofopticallycontrolledinterleavedstopbands(withdifferentmodespacing)canprovidemorecontroloverthedesiredregion(dashedbox)Inthiswork,theringresonatorissidecoupledtothemicrostriplineresultinginbadstopoperationTheseconfigurationsandmethodscanbeextendedtophotonicallycontrolledbandpassfiltersusingcapacitivegapcoupled(asopposedtosidecoupled)ringresonatorsOpticallycontrolledbandpassRFfilterswithrelativelylowinsertionlosscanbedesignedbyimplementingoptimizedcapacitivecouplingmethodsbetweenringsAlthoughforthesakeofsimplicityinthisproofofconceptdemonstration,weusedacollimatedbeamforilluminatingthesu

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