EML激光器

2007InternationalConferenceonIndiumPhosphideandRelatedMaterials9:30-9:45ConferenceProceedingsWeBI-419thIPRM14-18,May2007Matsue,JapanGaInNAsELECTROABSORPTIONMODULATEDLASERKenjiKoyama',Jun-ichiHashimoto'2,TakashiIshizukal2,YukihiroTsuji',TakashiYamada1'2,ChieFukudal,YutakaOnishil,KousukeFujiil,andTsukuruKatsuyamal21.TransmissionDevicesR&DLaboratories,SumitomoElectricIndustries,Ltd2.OptoelectronicsIndustryandTechnologyDevelopmentAssociation(OITDA)1,Taya-cho,Sakae-ku,Yokohama,244-8588,[e-mail]imefabricatedanelectroabsorptionmodulatedlaser(EML)withaGaInNAsmultiplequantumwell(MQW)activelayerusingthebutt-jointregrowthtechnique.Singlelongitudinalmodeoperationwithside-modesuppressionratio(SMSR)ofmorethan45dBupto120°Candtheextinctionratioofmorethan15dBupto100Cwereobtained.The2.5-Gb/suncooledoperationfrom25°Cto10oCwassuccessfullydemonstratedbychangingtheEAbiasvoltage.I.Introductionp-electrodeHRcoatingElectroabsorptionmodulatedlasers(EMLs),inwhichDFB//distributedfeedbacklaserdiodes(DFB-LDs)aremonolithicallyintegratedwithelectroabsorption(EA)modulators,aresuitableisolation-fortheuseinlong-haultransmissions,duetotheirsinglemode8__characteristics,compactness,highmodulationspeedandlowEAmodulaton-GaAschirp.Recently,EMLsareconsideredtobealsopromisingasa270pmcontactlayerlightsourceforhigh-speedandlarge-capacitymetro/accessZ-annetworks.Insuchapplications,uncooledoperationisrequiredforcladdinglayerthereductionsofcostandpower-consumption.i-AIGalnpConventionalEMLsaremadeofGalnAsP-relatedmaterialcurgrentblockinglayersystem.GaInAsPisawell-establishedmaterialwithhighaAgrtnlayercrystallinequalityandgoodreliability,howeverelectronji-GaInPcladdinglayerconfinement~inthacivlaeisweainthsmtraytmGainNAsDQWTherefore,opticaloutputpowerfromtheDFB-LDdecreaseARcoating//GainNAs6QWconsiderablyathightemperatureduetothecarrieroverflow.TheGaAssub.n-electrodeextinctionratiooftheBAmodulatoralsodecreaseathightemperatureduetothereductionofquantumconfinementstarkFig.1SchematicviewofaGainNAsEML.effects(QCSEs).Therefore,itisdifficulttorealizeanuncooledoperationintheconventionalEMLsconsistingofGaInAsPthebarrierlayersevenathightemperature.Therefore,thecarriermaterialsystem.Inrecentyears,AlGaInAs-basedEMLs[1]-[4]overflowcanbesuppressedeffectively,resultinginbetteraredevelopedtoovercomethisproblem,andshowimprovedtemperaturecharacteristics.Inadditiontothese,thefabricationcharacteristicsathightemperatureduetoabetterelectroncostoftheEMLchipcanbereduced,becauselow-costandlargeconfinementintheactivelayers.GaAssubstratescanbeusedinthismaterialsystem.However,fromaviewpointofmaterialsystem,EMLsusingInthisreport,weproposetheGaInNAs-basedEML,inGaInNAs[5]andtherelatedmaterialsseemtobethebestwhichDFBlaserismonolithicallyintegratedwithBAmodulatorcandidateforuncooledBMLs.Inthismaterialsystem,sincelargewithbutt-jointregrowthtechnique.Thegoodstaticbandgapmaterialssuchas(Al)GaAsor(Al)GaInPcanbeusedcharacteristicsand2.5-Gb/smodulationcharacteristicareforthebarrierlayers,electronscanbeconfinedinthewelllayerdemonstratedunderuncooledconditioninthetemperaturerangestronglybythelargebandgapdifferencebetweenthewellandfrom25°Cto1O0°C.1-4244-0875-X/07/$20.00©2007IEEE.365II.Devicestructureandfabrication1260AschematicviewofthefabricatedGaInNAsEMLisshown1250GainNAsDFB-LDinFig.1.Thedeviceconsistsofa270-,umEAmodulatorsection,[0.1nm/K]a80-1tmisolationsection,anda300-1tmDFBlasersection.All_1240AtheepitaxiallayersweregrownbylowpressureOMVPE.Inthe1230-Detuning(30nm)firstgrowth,aSi-GaInPcladdinglayer,anactiveregionsandwichedbetweenun-GaAsopticalconfinementlayers,aC:1220-a)Zn-GaInPetchingstoplayerandaZn-GaAsgratinglayerweregrownonann-GaAswafer.Theactiveregionconsistsofa121GaInNAsDQWandaGaAsbarrierlayer.OntheDFB-LDBiastuningsection,aBragg-gratingwasformedintheGaAsgratinglayer1200-anNAsEA(6QW)usingelectronbeamlithographyandwetetching.Aftergrowing1190[0.4nm/K]theZn-GaInPcladdinglayerontheGaAs-grating,theunnecessarylayersintheEAmodulatorsectionareremovedby1180wet-etching,andthentheactiveregionoftheEAmodulators255075100sectionwasformedusingaconventionalbutt-jointregrowthTemperature(°C)technique.TheactiveregionontheEAmodulatorsectionconsistsofaGaInNAs6QW.Afteraridge-stripestructurewasFig.3TemperaturedependenceoftheDFBwavelengthformedbywet-etchingoftheZn-claddinglayer,both-sidesoftheandtheEAabsorptionpeakwavelength.ridgewereburiedbyanSi-AlGaInPcurrent-blockinglayer.Finally,theremainingpartoftheZn-GaInPcladdinglayerandauniformoverthewholeregion.Thenon-uniformregionwithinZn-GaAscontactlayerwereovergrown.Afterforming..p-electrodes,ann-electrodeandisolationgroves,theBMLchipsfewicronssetotdevicelengthof65O0pm.weremadebycleavage,andARandHRcoatingswereperfrmedonteE-sidandtheDFB-LD-sidefacets,InordertooperatetheBMLinawidetemperaturerange,performedontheBA-sideandtheDFB-LD-sidefacets,wedesignedthedetuningbetweentheDFBwavelengthandtherespectively.Tospestimatevtheequaltlofythe.butt-jont,wemeasEAabsorptionpeakwavelengthtobeabout53nm(45meV)atphotolumnescence(PL)propertyaround