室温准连续多量子阱二极管激光器调谐特性

第8卷第2期2010年3月纳米技术与精密工程NanoteclmologyandPrecisionEngineeringV01.8No.2Mar.2010TunabilityofMultipleQuantum-WellDiodeLaserinQuasi-ContinuousWaveatRoomTemperatureDUZhen-hui,ZHAIYa—qiong,HUBo,QIRu.bin(StateKeyLaboratoryofPrecisionMeasuringTechnologyandInstruments,T/觚jinUniversity,Tianjin300072,ChinaAbstract:Inordertoteststrain—compensatedmultiplequantumwell(SC—MQWlasersfordetectionofgasmolecules,basedontunable—diode—laserabsorptionspectroscopy(TDLAS,thetunabilityofSC—MQWdiodelaserwasinvestigatedonquasi—continuouswave(QCWoperationatroomtemperature.Ap—plyingtherateequationofsemiconductorlaser,theeffectsoftheinjectedcurrentandthetemperatureontheoutputwavelengthofSC-MQWlaserswereanalyzed.Moreover,thetuningcharacteristicsofSC—MQWlaserdiodeatvarioustemperaturesandcurrentsweremeasuredwith盯一IRspectrometer.ResultsshowthatitCallbetunedtoabout20amwitharateofabout0.03nm/mAbychangingtheinjectedcurrentofthelaserdiode,andthetuningrateofthelaserdiodewithtemperatureisabout0.25nm/。C.TheoveralltuningrangeCallcover50nmbycombiningthecurrentandtemperaturetuning.SC—MQWdiodelaserprovestohavegoodapplicationprospectsfordetectinggasesofvolatileorganiccompoundswithband—likeabsorptioncharacteristics.Keywords:tunablediodelaser;tunability;quasi■-continuouswave;multiplequantum--welldiodelaser室温准连续多量子阱二极管激光器调谐特性杜振辉，翟雅琼，胡波，齐汝宾(天津大学精密测试技术及仪器国家重点实验室,天津300072摘要:为了将应变补偿多量子阱(SC.MQW激光器用于调谐激光吸收光谱(TDLAS技术进行气体分子检测,研究了SC-MQW激光器在宣温、准连续工作模式下的调谐特性.从半导体激光器的速率方程出发，分析了SC-MQW激光器输出波长与温度和注入电流的关系;使用傅里叶变换红外光谱仪(FT-IR测量了激光器分别在不同电流、温度条件下的调谐特性，得到SC-MQW激光器在允许工作电流范围内的调谐范围接近20am，电流调谐率约为0.03nm/mA;温度调谐率约为0.25nm/oC;电流和温度联合调谐的波长覆盖范围达50BIn.结果表明,该激光器在带状吸收谱的挥发性有机物气体检测方面有很好的应用前景.关键词:可调谐二极管激光器;调谐特性;准连续波;多量子阱二极管激光器中图分类号:0433.1;TN248.4文献标志码:A文章编号:1672-6030(2010-02-0126-06Thetechnologyoftunablediodelaserabsorptionspectroscopy(TDLASwithtunablediodelaser(TDLasit8coreelementCanbeusedinreal—timeon.1inemea8.urementandanalysisofgases.Duetoitshighsensitivity.excellentselectivity,smallvolumeandlowcost,ithasbeenwidelyappliedinfieldslikechemicalanalysis,en一vironmentaldetectionandscientiffcresearch【1.3].Atpresent,thetypesofTDLmainlyincludeleadsaltdiode收稿日期:2009—12-22.基金项目:国家高技术研究发展(863计划资助项目(2006AA062410;天津市自然科学基金资助项目(06YFJMJC06700作者简介:杜振辉(1967一，男，博士，副教授.通讯作者:杜振辉。duzhenhui@.ca.万方数据2010年3月杜振辉等:室温准连续多量子阱二极管激光器调谐特性(英文・127■laser,distributedfeedback(DFBdiodelaser,verticalcavitysurfaceemittinglaser(VCSELandquantumca8-cadelaser(QCL,etc‘4弓|.TheradiationwavelengthsofleadsaltdiodelaserandQCLlieinmid—infraredfinger-printregion,butthenecessityoflowtemperaturefortheiroperationhaslimitedtheirwideapplication(4巧1:thenear.infraredDFBdiodelaserwhichoff,hatesfromopticalcommunicationtechnologyhasexcellentmonochromaticityandstability,butitsselectableoutputwavelengthrangeissmall(between1.2斗mand1。6斗m,leadingtotheshorttuningrangeandweakabsorptionofthematerialtobedetected,therefore,itcanonlydetectfewkindsofga-sesoflowmolecularweightwithlineabsorption(CH4,HF,NH3,CO,C02,H20,etc..Thefundamentalos-cillatoryfrequencyoforganicmoleculesnormallyliesinthemid—infraredband(3斗m——20斗m,andtheabsorp-tionofnear—infraredspectramainlyincludesharmonicab-sorptionandsum—frequencyabsorption,whereasthesum—frequencyabsorptionusuallyliesinthewavelengthran99of2.0“m——2.5"mwhichistheidealwavebandforon—linemonitoringoforganicgasesinthesensethatthereisnoobstructionofwaterabsorptionandsum—frequencyab-sorptionishigherthanhigh—orderharmonicabsorptioninintensity.However.thesum—frequencyabsorptionofo卜ganicmoleculesusuallyshowsacharacteristicofband—likeabsorption,whichrequiresarelativelywiderangeofwavelengthforthespectrumanalyzer.AsthetuningrangeofpresentTDLisshort(1nm.2nmIs],itcanonlydetectcertainsegmentofband—likeabsorptionline,an—abletoimplementtheabsorption■-linediscerningtechnolo--gYwhichisadistinctivefeatureofTDLAS,whichmeanstIlatitisunabletodetectgaseswithband—likeabsorptioncharacteristics.Asaresult,itissignificanttoinvestigatethewide--rangetunabilityofLDatnear・-infraredbandof2.0pm—_2.5灿mfordetectingvolatileorganicgaseswithband-likeabsorptioncharacteristics.Thestrain—compensatedmulti-quantumwell(SC—MQWstructureofdiodelaserisabletoreducethresholdcurrentandimprovetemperaturecharacteristic,whichcanimproveitstunability.OnthetIleoreticalbasisoftherateequationofsemiconductorlasers,thepaper叽alyzIestheeffectsoftemperatureandcurrentonthetunabilityofSC.MQWdiodelasers,andproposestocombinetempera—tureandcurrenttuningtoexpandthetuningrangeofla-sers,whichisverifiedthroughexperiments.1AnalysisofthetunabilityofSC-MQWdiodelasersTheactivelayerofSC-■MQWdiodelaserisastruc--tureofstrain-compensatedmulti—quantumwell.Thequantumwellstructureisdevelopedwiththetechnologyofmetallorganicschemicalvapordeposition[9-10],whilequantumwelllasersareoflowthresholdcurrent,highquantumefficiencyandhiShoscillationfrequency,andcandirectlyworkunderrelativelyhightemperature.Theintroductionofstrainreducesthefinitemassofholesandfurtherreducesthetransitionbetweenvalencebands,sothethresholdcurTentofQWlasersissharplyreduced[11-123.Simultaneouslythequantumefficiency,theoscillationfrequency,andfurthermore,thetemperaturecharacteris—ticsareimproved80thatnon—refrigerationoperationofla-ser8canberealized.Moreover。thestraincompensationhasenhancedtheworklifeoflasersthroughimprovementofmaterialqualitr.Inaddition,strain—compensatedquantumwelllasershaveahighermodulationrateandcanreachalargertuningrangeunderpermittedworkingconditionthanaveragelasers.TherateequationofSC—MQWlasersisexpressedasfoilows[13|:idN=iJ—7°W—GS(1面dS=(G—ys+R叩,(2警一等(s圳一％tOFAn(3。whereNdenotesthecarrierconcentration,Sdenotespho一tondensity,咖denotesthephaseposition,Jdenotesthedensityofinjectedcurrent,ddenotesthethicknessofae一tirearea,edenotestheelectroncharge,7edenotesthecarrierrecombinationrate,Gdenotesthenetstimulatedemissionrate,7denotestheattenuationrateofphotons,R卵denotestheratechangecausedbycompositionofspontaneouslyemittedphotonstophotons,nMstandsformoderefractiveindex,ngstandsforgrouprefractivein—dex,(I'standsforradiationmodefrequency,力standsforcavityresonantfrequency,J1standsforthelimitingfactorsofmodefield,andAnstandsforthevariationofrefrac.tireindex.Thereisalinearrelationshipbetweenthevariationof万方数据-128-纳米技术与精密工程第8卷第2期refractiveindexAnandthechargecarderconcentrationIV[131:An=bN(4AconclusioncanbedrawnfromEqs.(3and(4:fordiodelasersbasedoninjectedcurrentpumping,thechangeincurrentcardercausedbychangeofinjectedcurrenthascausedthechangeofrefractiveindex,andfi—naUycausedthechangeofphasepositionofradiationmode.AsthephasepositioninrateEq.(3isselfcon—sistent,itprovesthatthechangeofrefractiveindexAncausedbycarderhasinfluencedtheradiationmodefre—quencyto.Inanotherword,thechangeofinjectedcur-rentwillchangetheradiationwavelengthoflasers,whichisatraditionalexplanationforthefundamentalprincipleofcurrenttuning.Asamatteroffact,theinfluenceofcurrent.inducedJouleheathasalsobeeninvolvedinthechangeoflasers’wavelengthcausedbyinjectedcurrent.Theformulaoftheradiationwavelengthofdiodela-8ersAisA=2nMI/M(5where,Zdenotesthelasercavitylength,andMisaposi—tiveinteger.Withtheincreaseofinjectedcurrent,thereisathermalexpansioninthelaserresonantcavity,andthentheradiationwavelengthwillmovetothedirectionoflongwavelength.Asaresult,thecurrenttuningoflasersisacombiningeffectofthecartierchangecausedbyin-jectedcurrentandthecavitylengthchangecausedbyJouleheat.Inaddition,thetemperatureofthelaserresonatorcanalsobechangedbyexternallyappliedheat,sothattheoutputwavelengthcanbechanged.Thechangeinra—diationwavelengthcausedbytemperaturechangeisalsoreflectedintwoaspects:firsty,thechangeoftemperaturecausesthechangeinrefractiveindexofsemi—conductormaterials;secondly,thechangeoftemperaturecausesthechangeinlasercavitylength.Temperaturetuningcanbeexpressedasfollows[141:而AA:尘f黑+砌1(6斫2il丽+叫(6’where,adenotesthecoeffleientofthermalexpansionofthematerialsinactivelayer.ThefirsttermintherightsideofEq.(6denotesthechangeofrefractiveindexcausedbyincreaseoftemperature,andthesecondde—notesthechangeofwavelengthcausedbythethermalex—pansionoflasercavity.Infact,theinfluenceofcurrentandtemperatureontheoutputwavelengthofdiodelaserliesnotonlyintherefractiveindexoftheactivelayerandthelasercavitylength,butalsointhetemperaturecharacteristicsofIlia—terialbandgap,whoseeffecthasnotbeentakenintocon—siderationhere.2ExperimentaldevicesThetestsystemforthetuningcharacteristicsofdiodelasersisshowninFig.1,whichadoptstheSC—MQWdi—odelasersproducedbyIBSGCompany.Thediodelaserworksinquasi—continuouswaveatroomtemperature,whoseradiationpoweris2.5mW,radiationwavelengthis2.2斗m,thresholdcurrentis21mA,themaximumworkingcurrentis120mAandtherangeofworkingtem-peratureis一5°C——20cC.Thelaserhasintegratedtwo—stagePeltierthermoelectriccoolerandthermistortempera-turesensor.LDC-3908(ILXLightwaveisusedtocontrolthecurrentandtemperatureofthelasers.TheFouriertransforminfrared(FrIRspectrometerSpectrumGX(PerkinElmerworksinthemodeofexternallightsourcetomeasuretheoutputmodespectrumofthelasers,andtheresolutionofthemeasurementis0.1cm~,therangeofscanningwavenumberis4500cm一1—300Cm-1.Fig.lBlockdiagramforthetestsystemofdiodelasertuningcharacteristics3ExperimentalresultsandanalysisThroughtheexperiment,thetuningrateandrangeofSC・-MQWlaserswithcurrentandtemperaturearerespec■■tivelyinvestigated,andthecombiningtuningrangewithcurrentandtemperatureisalsoresearched.3.1CurrenttuningThelaseriskeptunderafixedtemperature,andtheinjectedcurrentincreasedstepbystep,thenthelongitu-dinalmodespectrumundereachcurrentismeasured,万方数据2010年3月杜振辉等:室温准连续多量子阱二极管激光器调谐特性（英文・129■thatis,thecurrenttuningcharacteristicsareinvestigatedoFig.2showsthecurrenttuningcharacteristicsofthelaserunder15°C.Underacertaintemperature.withtheincreaseofinjectedcurrent,thewavelengthoftheradia—tionlasermovestothedirectionoflongwavelength.Whentheinjectedcurrentisatalowlevel,thelasershowsallexcellentcharacteristicofsinglelongitudinalmode.Andwhentheinjectedcurrentincreases,itturnsintomulti—longitudinalmodeoutput,withthedistancebetweenadjacentlongitudinalmodeas1.9nm(109GHz.Thecurrenttuningrateisabout0.03nm/mA.Inthepermittedrangeofworkingcurrent,thetuningrangeofabout20nmcanbeobtained.However,currenttuninginarelativelylargerangecallcausemodehoppingofthela-ser.Intherangeof30mA—100mAoftheinjectedcur-rent,twicemodehoppingtakesplaceintheoutputofthelaser.Inthenon—hoppingregion,thewavelengthofthelasershowsaquasi—linearchangewiththecurrentshowninFig.3.Theaveragecurrenttuningrateintherangeof30mA卅mAis0.0274nm/mA.intherangeof60mA——70mAis0.0296nm/mA.andintherangeof70mA一100mAis0.0355nm/mA.whichmeansthecur-renttuningrateriseswiththeincreaseofworkingcur-rent.BasedonEq.(5,theincreaseofcurrenttuningrateiscausedbytheJouleheateffectofthecurrent.Fig.2Energyspectraatdifferent蛳币ectedcurrentsAstheheateffectisproportionaltothesquareofcurrent,supposingthattherefractiveindexoftheactiveareaisinlinearrelationshipwiththeinjectedcurrent,themodelparameterofcurrenttuningaccordingtothequad—raticpolynomialstructureCallbeexpressedas五(i,r=u(Ti2+b(Ti+c(T(7where,a(T,b(Tandc(Trespectivelydenotesthemodelparametersofcurrenttuningatcertaintempera-Fig.3Modehoppingandtuningrateofcurrenttuningture.Whenthetemperatureofthelaseris15°C.thethreemodelparametersare3.7x10~.—2.6x10—4and2.1x10〜.respectively.Themodelstructureandparameterwereverifiedbyexperimentsatdifferenttemperaturesandinjectedcur-rents,asshowninFig.4.Exceptthedeviationinthemeasurementresultofthreeparametersincluding(0oC,50mA,(10C,50mAand(5oC,85mA,otherdataallshowanexcellentconsistencywiththecurrenttuningmode.Inaddition,themodelparametersatdiffer-enttemperaturesarethesame,whichmeansthatthecur-renttuningrateisirrelativetotemperature.Fig.4Currenttuningrateatdifferenttemperatures3.2TemperaturetuningThelaserissettoworkatacertaininjectedcurrent.TheinteriortemperatureofthelaseriscontrolledwiththePehierpartsintegratedinthelaserdiodemoduletoin-creasebyacertainstep,andthenthelongitudinalmodespectrumateachtemperatureismeasured,thatis,thetemperaturetuningcharacteristicsareinvestigated.Fig.5showsthemodespectraoftemperaturetuning.Fig.6showstherelationshipbetweenthetemperatureandthedominantmodewavelengthofthelaser.Withtheriseoftemperature,theoutputwavelengthofthelaserincrea-眄阱旺s侣任似他2222222010年3月■y■-二=^―=__—予三―thati&thecurrenttuningchted.Fig.2showsthecurrentti万方数据-130-纳米技术与精密工程第8卷第2期se¥,whichisexpressedasmulti—moderadiation.Withintherangeof0°C——20°C.atuningrangeof30amcanbeobtmned,andthetemperaturetuningrateisabout0.25nm/C.Inarelativelylargerangeoftemperature,therealeseveraltimesofmodehoppinginthelaser.Inthenon-hoppingregion,thewavelengthofthelasershowsaquasi-linearchangewiththetemperature.Thetempera—turetuningrateofthelaserinnon—-hoppingregionisre--spectively0.2nm/。C,0.26nm/。C,0.26nm/。C,0.25nm/%,0.26nm/。C,0.26nm/°C,0.24nm/°C,0.21nm/。Cand0.21nm/。C,andthemaximumtuningrangewithouthoppingis0.65am.Hereisthecombiningtuningwithtemperatureandcurrent.Thelaserissettoscanwithinthewholerangeofworkingtemperature,andatthesametimetheinjectedcurrentofthelaserisrapidlyscannedwithintherangeofworkingcurrent.Thismethodofsimultaneouslychangingthetemperatureandinjectedcurrentcanexpandthetun-ingrange.UndertheconditionsoftemperaturewithinO一20Candcurrentwithin30mA一100mA.atuningrangeofover50nInisobtainedbyusingthiskindofSC—MQWlaser.Tab.1showsthecurrenttuningrangewith-outmodehoppingatdifferenttemperatures.Fig.5Mode叩旧ctl噙ofia,鸵rdiodeatdifferenttempera-tures22902285毫:2”280,{2270区226522602255Range:2286.O睁一2286.30Range:2293.6I卜2283.90nI旷一Range:2279.2驴一2279.65面Range:2275.00_—2275.25.mm矗互272.45—2272.95nm厂厩最e:2268.10一2268.60Kill/"Range:2263.55—2264.20nmage:2259.30_—2259.70nm:2255.25—2255.45llm02468101214161820Temperamre/'Crig.6ModehoppingandtIlIIingratebytemper-aturettmi,,gTab.lCurrenttuningrangewithoutmodehoppingatvarioustemperaturesTempe—rature/°CMode—hopfreetuningrange/rim02243.05-2243.202246.90_2247.152250.90_2251.102254.90-2255.302259.10_2259.452265.25_2265.5552255.45—2255.852259.60—2259.952263.80—2264.102269.80—2270.202274.05—2274.40102260.30—-2260.502264.25—-2264.552268.35—-2268.602272.45—-2272.752274.70—-2274.952278.75—.2279.30152272.85—-2273.652279.40—-2279.652283.50—_2284.50202274.10_2274.202278.05q278.352284.20—2284.502288.35.2289.202293.10_2293.35Thepaperproposesthatsimultaneoustuningofcur-rentandtemperaturecanexpandthetuningrangeofSC■MQWlaserto50nm,sothereisanexcellentprospectforittobeappliedtodetectinggasmoleculeswithbroadbandabsorptionpeak.Moreover,thePeltierpartsembeddedinthelaserdiodemodulecanrealizerapidtemperaturescanning.Underadrivingcurrentof1A,thechangingrateoftemperaturecanexceed10。C/s.ActuallyweusedSC—MQWlasertodetectorganicgasessuchasmethyl■benzeneandpropane,andtillnowtheresolutionratioCallreachthemagnitudeof10-6.InadditionothisSC.MQWlasercallalsobeappliedtodetectingmoleculesoflineabsorption.Arita[15.16。proposedthetheoryandtech—nologyofmulti■modelaserstodetecttracegases.Inthemode—hopping—freetuningrangeofmuhimodelasers,eachmoderespectivelyscanstheadjacentgasabsorptionlineinproperorder,andthismethodcanalsobringabouthighresolutionratio.Therefore.theSC-MQWlaserwithawidetuningrangecanbeusedasthelightsourceinTDLASsystemtodetectthegasmoleculeswithlineab—sorptionandband.1ikeabsorptioncharacteristics.4ConclusionsSC—MQWdiodelasershaveanexcellenttunabilitybycurrenttuningandtemperaturetuningin*130*ses,whichisexpressedasmultitherangeof0—20P,atuiquasi■■contin■-万方数据2010年3月杜振辉等：室温准连续多量子阱二极管激光器调谐特性（英文）-131-UOUSwaveatroomtemperature.Underthepermittedcurrentcon—[7]LsekiT.AportableremotemethanedetectorusingallIn—ditionofinjectedandtempe

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