双异质结结构提高了半导体光源的量子效率课件

Fiber-OpticCommunicationTechnologyChapter3OpticalTransmittersFiber-OpticCommunicationTech2023/10/7OE,HUST2Chapter3.OpticalTransmittersIntroductionBasicconceptsSemiconductorlasers(LaserDiode)LaserCharacteristicsLight-EmittingDiodes(LED)TransmitterDesign2023/10/6OE,HUST2Chapter3.2023/10/7OE,HUST3Opticaltransmitter：光发射机LED:发光二极管LD：激光二极管Spontaneousemission：自发辐射Stimulatedemission：受激发射Stimulatedabsorption：受激吸收Boltzmanstatistics：玻尔兹曼统计分布Thermalequilibrium：热平衡Spectraldensity：光谱密度Populationinversion：粒子数反转Fermi-Diracdistribution：费米狄拉克分布Conductionband：导带Valenceband：价带Forward-biased：正向偏置Junction：结Fermilevel：费米能级Bandgap：带隙Heavydoping：重掺杂Homojunction：同质结Heterojunction：异质结Doubleheterostructure：双异质结Electron-holerecombination：电子空穴复合Claddinglayer：包层Augerrecombination：俄歇复合Kineticenergy：动能Nonradiativerecombination：非辐射复合Surfacerecombination：表面复合Internalquantumefficiency：内量子效率Directbandgap：直接带隙Indirectbandgap：非直接带隙Carrierlifetime：载流子寿命Latticeconstant：晶格常数Ternaryandquaternarycompound：三元系和四元系化合物Substrate:衬底LPE：液相外延VPE：汽相外延MBE：分子束外延MOCVD：改进的化学汽相沉积MQW:多量子阱2023/10/6OE,HUST3Opticaltran2023/10/7OE,HUST4Electron-holepairs电子空穴对Externalquantumefficiency外量子效率Fresneltransmissivity菲涅耳透射率Lambertiansource朗伯光源Power-conversionefficiency功率转换效率Wall-plugefficiency电光转换效率Responsivity响应度Rateequation速率方程Surface-emitting表面发射Beamdivergence光束发散Edge-emitting边发射Resonantcavity谐振腔Gaincoefficient增益系数Differentialgain微分增益Laserthreshold激光阈值Thresholdcurrent阈值电流Groupindex群折射率Externalcavity外腔Broadarea宽面Stripegeometry条形Diffusion扩散Index-guided折射率导引Ridgewaveguidelaser脊波导激光器Buriedheterostructure掩埋异质结Lateral侧向Transverse横向SLM:SingleLongitudinalmode单纵模MSR:Modesuppressionratio模式抑制比DFB:DistributedFeedback分布式反馈Braggdiffraction布拉格衍射Braggcondition布拉格条件DBR:distributedBraggreflector分布式布拉格反射器Phase-shiftedDFBlaser相移DFB激光器Gaincoupled增益耦合Coupledcavity耦合腔2023/10/6OE,HUST4Electron-hol2023/10/7OE,HUST5Superstructuregrating超结构光栅VCSEL:verticalcavitysurface-emittinglasers垂直腔表面发射激光器Photonlifetime光子寿命Spontaneous-emissionfactor自发辐射因子Characteristicstemperature特征温度Slopeefficiency斜率效率Differentialquantumefficiency微分量子效率Linewidthenhancementfactor线宽加强因子2023/10/6OE,HUST5Superstructu2023/10/7OE,HUST63.1Introduction3.1.1ComponentsofOpticalTransmittersBinarytosingleCoding/linecodingModulatorOpticalSourceDrivingCircuitPCMChannelcouplerOpticalsignaloutput2023/10/6OE,HUST63.1Introduc2023/10/7OE,HUST7BiasedcurrentModulationcurrent(≥10Gb/s)ModulationcurrentBiasedcurrent(≤2.5Gb/s)(a)DirectModulation(b)ExternalModulation2023/10/6OE,HUST7Biasedcurre2023/10/7OE,HUST81.stability:power&wavelength2.reliability:>25years(PouttoPout/2)3.smallemissiveareacompatiblewithfibercoredimensions4.rightwavelengthrange0.85µm:GaAlAs/GaAs1.31µm,1.55µm:InP/InGaAsP5.narrowlinewidth→dispersion,phasenoise6.directmodulation!?7.highefficiency&lowthreshold:MQW-LD,Ith~10mA3.1.2RequirementsforOpticalSourceMQWDFBLD2023/10/6OE,HUST81.stability2023/10/7OE,HUST9Chapter3.OpticalTransmittersIntroductionBasicconceptsSemiconductorlasers(LaserDiodes)LaserCharacteristicsLight-EmittingDiodes(LED)TransmitterDesign2023/10/6OE,HUST9Chapter3.2023/10/7OE,HUST103.2.1Threefundamentaltransitionprocesses 1.SpontaneousEmission→LED 2.StimulatedEmission→LD,SOA 3.StimulatedAbsorption→PIN/APD

3.2BasicConceptsLightEmission2023/10/6OE,HUST103.2.1Three2023/10/7OE,HUST113.2.2EmissionandAbsorptionRatesE2N2N1E1:spectraldensityoftheelectromagneticenergyInthermalequilibrium,accordingtoBoltzmannStatistics:kB:BoltzmannConstantT:AbsoluteTemperatureAccordingtoPlanck’sformula:2023/10/6OE,HUST113.2.2Emiss2023/10/7OE,HUST12visibleornear-infraredregion,roomtemperature,thermalsourcesN2>N1,Rstim>Rabs(populationinversion)thermalequilibrium laseroperation ?Operationconditionforlaser:Externalpumpingsourceisneeded:injectioncurrent,pumpinglightetc.2023/10/6OE,HUST12visibleor2023/10/7OE,HUST13原子是由原子核和绕原子核旋转的电子组成。最里层的电子距原子核最近，受原子核束缚最强，能量最低（包括电子的动能和势能）。越外层的电子受原子束缚越弱，能量越高；电子只能处于特定的能级之上；能级图用一系列高低不同的水平横线来表示电子所能取的确定能量；原子中的电子通过和外界交换能量的方式发生能级的跃迁——热跃迁和光跃迁。Energybandsinsemiconductorconductionband&valenceband2023/10/6OE,HUST13原子是由原子核和绕原子2023/10/7OE,HUST14实际物体是由大量原子构成的，每一原子的电子特别是外层电子除受本身原子的势场作用外，还受到相邻原子的作用。半导体材料中原子在共价键的作用下形成紧密相间、周期排列的晶格结构。电子能级受晶格作用发生分裂而形成能带；Si2023/10/6OE,HUST14实际物体是由大量原子构2023/10/7OE,HUST15价带：由共价键束缚的价电子所占据的能带为价带；导带：由自由电子占据的能带为导带，导带位于价带之上；禁带：导带和价带之间被宽度为Eg的带隙分开，称为禁带；绝缘体：Eg～7eV，电子不容易跃迁到导带；半导体：Eg～1eV，电子容易跃迁到导带；导体：Eg～0eV，没有带隙。2023/10/6OE,HUST15价带：由共价键束缚的价2023/10/7OE,HUST16EnergybandsinsemiconductorrecombinationbetweenelectronsandholesTheoccupationprobabilityforelectronsintheconductionandvalencebandsisgivenbytheFermi-Diracdistributions:Efc,EfvaretheFermilevelsinconductionbandandvalencebandrespectively2023/10/6OE,HUST16Energyband2023/10/7OE,HUST17:jointdensityofstates,whichdescribethenumberofstatesperunitvolumeperunitenergyrangeEg:bandgapmr:reducedmassmc,mv:effectivemassesofelectrons&holesinconductionandvalencebands,respectively2023/10/6OE,HUST17:jointde2023/10/7OE,HUST18population-inversioncondition:

inthermalequilibrium:pumpingenergyintosemiconductorbyinjectingcurrent

Togetlaseroutput,2023/10/6OE,HUST18population-2023/10/7OE,HUST191.

TypeofsemiconductorIntrinsicsemiconductor:undoped,Fermilevelislyinginthemiddleofthebandgapn-typesemiconductor:Fermilevelmovestowardtheconductionbandasthedopantconcentrationincreasesp-typesemiconductor:Fermilevelmovestowardthevalencebandasthedopantconcentrationincreases3.2.3p-njunctions2023/10/6OE,HUST191.Typeof2023/10/7OE,HUST20

n-typeIntrinsic

p-typeforwardbiasedp-typesemiconductor

&n-typesemiconductor2023/10/6OE,HUST20n-typeIntr2023/10/7OE,HUST21(a)inthermalequilibrium(b)underforwardbiased2.p-njunctionsunderforwardbiased:built-inelectricfieldisreduceddiffusionofelectronsandholesacrossthejunctionelectronsandholesarepresentsimultaneouslyindepletionregiongeneratelightthroughspontaneousemissionorstimulatedemissioninthermalequilibrium:

theFermilevelmustbecontinuousacrossthep–njunctionachievedthroughdiffusionofelectronsandholesacrossthejunction.2023/10/6OE,HUST21(a)inther2023/10/7OE,HUST22Homojunction:equalbandgapsthesamesemiconductormaterialwideregionforelectron-holerecombinationdifficulttorealizehighcarrierdensitiesHeterojunction:differentbandgapsDouble-heterojunction:

sandwichingathinlayerbetweenthep-typeandn-typelayerssuchthatthebandgapofthesandwicheslayerissmallerthanthelayersurroundingit.4.Homojunction&heterojunction2023/10/6OE,HUST22Homojunctio2023/10/7OE,HUST232023/10/6OE,HUST232023/10/7OE,HUST24Activelayer:lightisgeneratedinsideitasaresultofelectron-holerecombinationhigherdensityofcarriers→higherindex→waveguide(1D)Heterojunction:confinementofcarriers&opticalfield0.85µm:cladding/active:GaAlAs/GaAs1.31µm,1.55µm:cladding/active:InP/InGaAsP2023/10/6OE,HUST24Activelaye2023/10/7OE,HUST251.electron-holerecombination3.2.4NonradiativeRecombinationTrapofdefectsSurfacerecombinationAugerNonradiativerecombination2023/10/6OE,HUST251.electron2023/10/7OE,HUST262.internalquantumefficiencyRrr:radiativerecombinationrateRnr:nonradiativerecombinationrateRtot:totalrecombinationrateτ:recombinationtimeNonradiativerecombination,especiallyAugerrecombination(temperaturedependent)isharmfultodevices!positivefeedback

2023/10/6OE,HUST262.internal2023/10/7OE,HUST27E0E0k1k2(1)direct-bandgap(GaAs,InP)(2)indirect-bandgap(Si,Ge)3.carrierlifetimeA:defects&trapsB:spontaneousradiationC:Auger2023/10/6OE,HUST27E0E0k1k2(1)2023/10/7OE,HUST28Qualityoftheheterojunctioninterfacedependsonthelatticeconstantofthetwomaterials.(matching!)3.2.5SemiconductorMaterialsternarycompound2023/10/6OE,HUST28Qualit2023/10/7OE,HUST29quaternarycompound0.85µm:GaAlAs/GaAs(cladding/active)

1.31µm,1.55µm:InP/InGaAsP(cladding/active)2023/10/6OE,HUST29quaternary2023/10/7OE,HUST302023/10/6OE,HUST302023/10/7OE,HUST31Chapter3.OpticalTransmittersIntroductionBasicconceptsSemiconductorlasers(LaserDiodes)LaserCharacteristicsLight-EmittingDiodes(LED)TransmitterDesign2023/10/6OE,HUST31Chapter3.2023/10/7OE,HUST323.3Semiconductorlasers(LaserDiodes)Advantagesofstimulatedemissioncomparedwithspontaneousemissionofsemiconductormaterialsemittinghighpower(to100mW)narrowangularspreadnarrowspectralwidthdirectmodulationathighfrequency(to10GHz,becauseissmall)2023/10/6OE,HUST323.3Semicon2023/10/7OE,HUST33ComponentsofSemiconductorLasers2023/10/6OE,HUST33Components2023/10/7OE,HUST34z=0z=LInjectioncurrentGainmediumResonantcavityResonantcavityModeloflaser2023/10/6OE,HUST34z=0z=LInjec2023/10/7OE,HUST353.3.1OpticalGainPeakgainofmedium:

when :differentialgain(gaincrosssection) :injectioncarrierdensity :transparentcarrierdensity:thresholdcarrierdensityNTisequaltoNth?2023/10/6OE,HUST353.3.1Optic2023/10/7OE,HUST36Figure3.9:(a)Gainspectrumofa1.3-μmInGaAsPlaseratseveralcarrierdensitiesN.(b)Variationofpeakgaingp

withN.Thedashedlineshowsthequalityofalinearfitinthehighgainregion.Blueorredshiftingofpeakwavelengthwheninjectedcurrentincreases?2023/10/6OE,HUST36Figure3.9:2023/10/7OE,HUST373.3.2FeedbackandLaserThresholdFeedbackR1R2n0=1n2023/10/6OE,HUST373.3.2Feedb2023/10/7OE,HUST38Threshold2023/10/6OE,HUST38Threshold2023/10/7OE,HUST39AmplitudeconditionPhaseconditionspacingofoscillatingfrequencyoscillatingfrequencythresholdgainMLM2023/10/6OE,HUST39Amplitudec2023/10/7OE,HUST403.3.3LDStructuresBroad-areaLDFigure3.12:Abroad-areasemiconductorlaser.Theactivelayer(hatchedregion)issandwichedbetweenp-typeandn-typecladdinglayersofahigher-bandgapmaterial.light-confinementmechanisminthedirectionperpendiculartothejunctionplaneintroducedbydoubleheterostructure

XYdistributioninnearfield2023/10/6OE,HUST403.3.3LDSt2023/10/7OE,HUST41nosuchlight-confinementmechanisminthelateraldirectionparalleltothejunctionplane.thelightgeneratedspreadsovertheentirewidthofthelaser.relativelyhighthresholdcurrentandaspatialpatternthatishighlyellipticalandthatchangesinanuncontrollablemannerwiththecurrent.Howaboutspatialmodeinwaveguideanddistributioninfarfield?2023/10/6OE,HUST41nosuchlig2023/10/7OE,HUST42Gain-guidedsemiconductorlasersFigure3.13:Crosssectionoftwostripe-geometrylaserstructuresusedtodesigngain-guidedsemiconductorlasersandreferredtoas(a)oxidestripeand(b)junctionstripe.Stripelasers

XY2023/10/6OE,HUST42Gain-guide2023/10/7OE,HUST43solvethelight-confinementproblembylimitingcurrentinjectionoveranarrowstripe.thespotsizeisstillnotstableasthelaserpowerisincreased.Injectioncurrentinducedindexvariety!2023/10/6OE,HUST43solvethel2023/10/7OE,HUST44Index-guidedsemiconductorlasersFigure3.14:Crosssectionoftwoindex-guidedsemiconductorlasers:(a)ridge-waveguidestructureforweakindexguiding;(b)etched-mesaburiedheterostructureforstrongindexguiding.

XY2023/10/6OE,HUST44Index-guid2023/10/7OE,HUST45Multi-Quantum-WellLD有源区厚度薄1~10nm周期结构，将窄带隙的很薄的有源区夹在宽带隙的半导体材料之间，形成势能阱多个势能阱--多量子阱（MQW）2023/10/6OE,HUST45Multi-Quant2023/10/7OE,HUST46homojunctionDoubleheterostructureStripegeometryMulti-quantum-wellRelativelystrongerconfinementofinjectedcarriersandoutputphotons,thuslowerthresholdcurrent,andhigherslopeefficiency!2023/10/6OE,HUST46homojunctio2023/10/7OE,HUST473.3.4ControlofLongitudinalModesSideModeSuppressionRatio(SMSR):orMLMLossSLM2023/10/6OE,HUST473.3.4Contr2023/10/7OE,HUST48DistributedFeedback(DFB)Lasers

相位光栅在波导中产生折射率的周期性变化，使正反向传播的行波产生耦合。当光波长满足布拉格条件时，耦合达到最大。在布拉格条件下，某一入射波长几乎被全反射，光栅起到了对波长选择性反射的作用。光栅周期满足：2023/10/6OE,HUST48Distributed2023/10/7OE,HUST49Coupled-cavitylaserFigure3.18:Coupled-cavitylaserstructures(a)external-cavitylaser;(b)cleaved-coupledcavitylaser;(c)multisectionDBRlaser.2023/10/6OE,HUST49Coupled-cav2023/10/7OE,HUST50

增益介质反射镜准直透镜透镜光纤增透膜滤光片高反膜λcExternalcavitylaser2023/10/6OE,HUST50增益介质反2023/10/7OE,HUST51SampledGratingDBRLaserDBR:distributedBraggreflector2023/10/6OE,HUST51SampledGra2023/10/7OE,HUST52Cleaved-coupledcavitylaser2023/10/6OE,HUST52Cleaved-cou2023/10/7OE,HUST53VCSEL2023/10/6OE,HUST53VCSEL2023/10/7OE,HUST54思考题1.现有半导体激光器的F-P谐振腔，长度为400

m，材料折射率为3.5，谐振腔两端面一端镀有增反射膜，反射率为90％，另一端没有镀膜。现有半导体激光器工作在1550nm附近，要求谐振腔谐振的阈值增益系数小于75cm－1，请问：如何选择半导体材料和组分？谐振腔内部损耗系数应满足什么条件？2023/10/6OE,HUST54思考题1.现有半导体2023/10/7OE,HUST55Chapter3.OpticalTransmittersIntroductionBasicconceptsSemiconductorlasers(LaserDiodes)LaserCharacteristicsLight-EmittingDiodes(LED)TransmitterDesign2023/10/6OE,HUST55Chapter3.2023/10/7OE,HUST563.4LaserCharacteristics

3.4.1CWCharacteristicsForaSLMlaser,therateequations:P,N:numberofphotons&carriersNetrateofstimulatedemission—opticalgain:g:peakgainofmaterial:gaincrosssection,ordifferentialgain.Photonlifetime:2023/10/6OE,HUST563.4LaserC2023/10/7OE,HUST57Thresholdofcurrent&carrierForI>Ith(R1=R2)CWoperation:2023/10/6OE,HUST57Thresholdo2023/10/7OE,HUST58ThresholdofP-IcurvesSpontaneousemissionStimulatedemissionI0:constantT0:characteristictemperatureGaAs:T0=120K,InGaAsP:T0=50~70KP-IcurvesBendingofP-Icurves

Rnr:mainlydependingonAugerrecombinationinInGaAsPLDsSolution:built-inthermoelectriccoolerisusedtodealwithtemperaturesensitivitiesofInGaAsPLDs2023/10/6OE,HUST58Thresholdo2023/10/7OE,HUST59EfficienciesInternalquantumefficiency:Slopeefficiency:Differentialquantumefficiency:Externalquantumefficiency:wall-plugefficiency:2023/10/6OE,HUST59Efficiencie2023/10/7OE,HUST603.4.2Small-SignalModulationsmall-signalmodulation:Frequencyresponse2023/10/6OE,HUST603.4.2Small2023/10/7OE,HUST61Figure3.21:Modulationresponseofalaserasafunctionofmodulationfrequencyatseveralbiaslevels.ModulationbandwidththeefficiencyisreducedwhenthemodulationfrequencyexceedsΩR

byalargeamount.2023/10/6OE,HUST61Figure3.212023/10/7OE,HUST623.4.3Large-SignalModulationExternalmodulationforhighspeedtransmission!Frequencychirp

leadingedge:modefrequencyshiftstowardtheblue

sidetrailingedge:modefrequencyshiftstowardtheredside:amplitude-phasecouplingparameter,ex.bulkmaterial:4~8;MQW:~32023/10/6OE,HUST623.4.3Large2023/10/7OE,HUST63Electro-opticalDelay&RelaxationOscillation

Pre-biasedtoreducedelaytime!请参见江剑平编著的《半导体激光器》2023/10/6OE,HUST63Electro-opt2023/10/7OE,HUST64Patterneffect

TBIP“11”“11”当电光延迟时间与电调制速率对应的的码元持续时间相近时，会使“0”码后的第一个“1”码脉冲宽度变窄，幅度变小，严重时使单个“1”码丢失，这种现象即“码型效应”。连“0”数越多，调制速率越高，该效应越明显。用适当的“过调制”补偿，可以消除码型效应。2023/10/6OE,HUST64Patterneff2023/10/7OE,HUST65Self-pulsation不同于张弛振荡，没有阻尼，脉动频率范围为0.2~4GHz容易发生在阈值附近和P-I特性的扭曲区造成自脉动的机理涉及量子噪声效应、有源区的缺陷及温度感应的变化等因素抑制这种现象主要靠控制材料的质量，尽量减少有源区的缺陷。Operatedfarfromkinkzone!OPIPI2023/10/6OE,HUST65Self-pulsat2023/10/7OE,HUST66Simulation1-Directmodulation2023/10/6OE,HUST66Simulation2023/10/7OE,HUST67Simulation2-Externalmodulation

2023/10/6OE,HUST67Simulation2023/10/7OE,HUST68Ib&ImLD偏置电流的选择合适与否直接影响激光器的高速调制输出特性。加大直流偏置，使其接近阈值，可以减小电光延迟时间，也可使张驰振荡得到一定程度的抑制。当激光器偏置在阈值附近时，较小的调制电流就能得到足够高的输出光脉冲，调制效率较高。而且由于偏置电流与最大电流相差不大，可以大大减小码型效应和结发热效应的不良影响。过大的偏置电流会使消光比恶化，影响接收机灵敏度。激光器恰好偏置在阈值时，散粒噪声会增强，直接影响信号的信噪比。2023/10/6OE,HUST68Ib&ImLD偏置2023/10/7OE,HUST69Chapter3.OpticalTransmittersIntroductionBasicconceptsSemiconductorlasers(LaserDiodes)LaserCharacteristicsLight-EmittingDiodes(LED)TransmitterDesign2023/10/6OE,HUST69Chapter3.2023/10/7OE,HUST703.5.1Power-CurrentCharacteristics3.5Light-EmittingDiodes(LEDs)aforward-biasedp-njunction→spontaneousemission→LED2023/10/6OE,HUST703.5Light-E2023/10/7OE,HUST712023/10/6OE,HUST712023/10/7OE,HUST72Power-conversionefficiency(wall-plugefficiency)2023/10/6OE,HUST72Power-conve2023/10/7OE,HUST73P-ICurveResponsivity:(1)responsivityremainsconstantwhenIissmall(2)bendingofP-Icurve:(3)nothreshold

2023/10/6OE,HUST73P-ICurveRe2023/10/7OE,HUST743.5.2LEDSpectrumanapproximateexpression:LEDsaresuitableforLANwithlowbitrate&shortdistance!2023/10/6OE,HUST743.5.2LEDS2023/10/7OE,HUST75Figure3.7:(b)spectrumoftheemittedlightforatypical1.3-μmLED.超宽带光源白光LED2023/10/6OE,HUST75Figure3.7:2023/10/7OE,HUST762023/10/6OE,HUST762023/10/7OE,HUST773.5.3ModulationResponseRateequation::injectioncarrier:carrierofrecombination(nonradiative&spontaneousemission)Sinusoidalmodulation:Ib:biascurrentIm:modulationcurrentωm:modulationfrequency2023/10/6OE,HUST773.5.3Modul2023/10/7OE,HUST78Sincemodulatedpowerisrelatedtolinearly2023/10/6OE,HUST78Sincemodul2023/10/7OE,HUST793.5.4LEDStructures(a)(b)(a)surface-emittingLED(b)edge-emittingLED2023/10/6OE,HUST793.5.4LEDS2023/10/7OE,HUST80思考题1.以下论述正确的是：（）A、非辐射复合会影响发光器件的发光效率；B、正向偏置的PN结中导带和价带的准费米能级趋于一致；C、半导体材料要发光，必须实现粒子数的反转；D、LED中最初的光子来源于内部的自发辐射；E、电子与空穴复合不一定产生光子；F、双异质结结构提高了半导体光源的量子效率；G、工作于1.55

m处的半导体光源有源层材料为InP；

H、温度升高发光器件的发光效率会下降；

I、间接带隙半导体材料中非辐射复合效率高于辐射复合效率，不适合用作光源材料。2023/10/6OE,HUST80思考题1.以下论述正2023/10/7OE,HUST811.以下论述正确的是：（）

A、非辐射复合会影响发光器件的发光效率；

B、正向偏置的PN结中导带和价带的准费米能级趋于一致；C、半导体材料要发光，必须实现粒子数的反转；

D、LED中最初的光子来源于内部的自发辐射；

E、电子与空穴复合不一定产生光子；

F、双异质结结构提高了半导体光源的量子效率；G、工作于1.55

m处的半导体光源有源层材料为InP；

H、温度升高发光器件的发光效率会下降；

I、间接带隙半导体材料中非辐射复合效率高于辐射复合效率，

不适合用作光源材料。2023/10/6OE,HUST811.以下论述正确的是2023/10/7OE,HUST82A、LD的激射波长一定是自发辐射的峰值波长；B、条形激光器中也存在双异质结结构；C、双异质结中对载流子的限制作用是因为存在内建折射率波导；D、通过选择合适的组分x和y，基于In1-xGaxAsyP1-y的半导体光源可设计工作于0.85

m处；E、LD有谐振腔，而LED没有；F、LD的P-I曲线有阈值，而LED的P-I曲线没有阈值；G、LD和SOA中最初的光子均来源于自发辐射；H、激光器的小信号调制带宽会随着偏置电流的增加而增大；I、偏置电流选择合理可适当减小张驰振荡和电光延时效应的影响；J、单纵模LD用作光源时，色散容限大。

2.以下关于半导体材料和发光机理论述错误的是：2023/10/6OE,HUST822.以下关于半导体2023/10/7OE,HUST83

A、LD的激射波长一定是自发辐射的峰值波长；B、条形激光器中也存在双异质结结构；

C、双异质结中对载流子的限制作用是因为存在内建折射率波导；

D、通过选择合适的组分x和y，基于In1-xGaxAsyP1-y的半导体光源可设计工作于0.85

m处；E、LD有谐振腔，而LED没有；F、LD的P-I曲线有阈值，而LED的P-I曲线没有阈值；

G、LD和SOA中最初的光子均来源于自发辐射；H、激光器的小信号调制带宽会