半导体放大器双稳的毕业论文

目录目录II.GAINANDBANDWIDTHAcommonmodelingapproachtoverticalcavitylasersisthereplacementoftheDBRsbyhardmirrorsofthesamereflectivitywhichareseparatedbyaneffectivecavitylengthLc.Thisway,wecanstartwiththewellknowngainformulasofFabry-Perotamplifiers(GR-reflectionmode,GT-transitionmode)withthefrontmirrorreflectivityRf,thebackmirrorreflectivityRb,thesinglepassgainGs,andthesinglepassphasedetuningΦ.ThemaximumgainisachievedwithΦ=0,whenthesignalwavelengthisidenticaltotheFabry-Perotresonance.VCLAsexhibitmuchsmallervaluesGsandlargerreflectivitiesthanin-planedevices.ForVCLAs,thepeakreflectivityoflosslessDBRswithmperiods(2mlayers)isgiven.usingthelow-to-highrefractiveindexratiosofthetwoDBRlayers(p),aswellasatthefirst(q)andthelast(a)DBRinterface.Assumingrefractiveindicesof3.45(GaAs)and2.89(AlAs),wecalculateRf=0.985andRb=0.999forourdevice.Absorptionordiffractionwithinthemirrorreducesthereflectivity.ThewavelengthdependenceoftheDBRreflectivityisignoredheresincethereflectionbandwidthoftypicalDBRsismuchlarger(about100nminourcase)thantheamplifierbandwidthandthecavityresonancewavelengthλcisassumedidenticaltotheDBRcenterwavelength.Ourone-dimensionalmodelalsoneglectsthetransversalopticalmodestructure.Resonancewavelengthsdifferslightlyamongtransversalmodes.ThephaseΦinEqs.1-2givesthedeviationofthesignalwavelengthλfromλc.withthecavityrefractiveindexnc.TheeffectivecavitylengthLcislargerthantheDBRdistanceLmanditincludesthephasepenetrationdepthsLfandLbintofrontandbackDBR,respectively(Lc=Lf+Lm+Lb).ThephasepenetrationdepthLpofalosslessDBRatcenterwavelengthλcisgiven.Withnc=3.2,theDBRpenetrationdepthinourdeviceisabout585nm,resultingintheeffectivecavitylengthLc=2.2μm.Duetothehighindexcontrast,AlAs/GaAsDBRsexhibitsmallerpenetrationdepthsthanmirrorsgrownonInP.ThecavityrefractiveindexncisobtainedbyaveragingoveralllayersbetweenthetwoDBRs.Typically,itissomewhathigherthantherefractiveindexofthespacermaterial(InP)atthetargetwavelength,however,itcanbeaffectedbythequantumwellcarrierdensityaswellasbydeviceheating.TheremainingparameterinEqs.1-2tobediscussedisthesinglepasssignalgainGs.Assuminglaterallyuniformmaterialpropertiesacrossthesignalspot,thesinglepassgaininaVCLAiscalculatedfromtheactiveregionmaterialgaingbywiththegainenhancementfactorξ(ξ<2),thetotalthicknessLaofallquantumwells,andtheaveragecavitylosscoefficientαc.Gainenhancementresultsfromtheplacementoftheactiveregion(s)atthepeak(s)ofthestandingopticalwavewith[14](LMQW-thicknessofeachMQWstack).Wecalculateξ=1.75forourperiodicgainstructure.ComputationofthequantumwellmaterialgaingisthemainchallengeofVCLAmodeling.TheopticalgaindependsontheQWcarrierdensityN,thesignalwavelengthλ,thetemperatureT,andthephotondensityS.Assumingλ=λc,roomtemperature,andrelativelylowphotondensities,thequantumwellgaincanbeapproximatedbyTheseformulasgivethefullwidthathalfmaximum(-3dB).Ingeneral,thebandwidthdecreasesasthepeakgainincreases.Thesquarerootofthepeakgaintimesthebandwidthgiveafigureofmeritthatispracticallyconstant(gain-bandwidthproduct).Thethresholdconditionandtheapproximationsin(x)=x(forsmallx)leadstothesimpleformulas.TheseequationsarevalidforanyFabry-Perotamplifierandtheirresultsareidenticalforsymmetricaldevices(Rf=Rb).Inthereflectioncase,Eq.11isrestrictedtogainvalueswellabove3dBsincetheinitialreflectioncausesasingularityofEq.9.Remarkably,thegain-bandwidthproductinreflectionmodedoesnotdependonthebottomreflectivityRbandgain-bandwidthmeasurementscanbeusedtoverifythefrontreflectivityRfortheopticalcavitylengthncLc.Figures3and4plotthegain-bandwidthproductasfunctionoftheoutputmirrorreflectivityforreflectionandtransmissionmode,respectively.ThedotsinFig.3givemeasuredresultsofour1.3µmVCLAswhichconfirmourmodel.Lowerreflectivitygiveshigherbandwidthinbothcases.Thereflectionmodecurvecrossestransmissionmodecurvesforsymmetricdevices(Rf=Rb).Thisleadstotheintuitiveresultthatthetransmissionmodegivesahighergain-bandwidthproductthanthereflectionmodeifRb<Rf(andviceversa).外文资料译文

外文资料译文半导体激光放大器的建模与优化二．增益和带宽对垂直腔激光器一个常见的建模方法是由具有相同的反射率的，有效腔长度为LC，分开的平面镜来代替DBRS。这样，我们就可以从著名的法布里珀罗特放大器增益公式的开始研究（GR反射模式，GT转换模式）前镜反射率为Rf、后镜反射率Rb、单程增益GS，和单通道相位失谐Φ。当信号的波长与法布里珀罗特谐振波长相同时，最大增益是Φ=0。相比与平面器件，vclas具有更小的GS和较大的反射率。使用两层DBR从低到高的折射率比值，同时也加入第一（q）和第二（a）的DBR界面。假设使用折射率为3.45的（GaAs）和折射率为2.89（AIAs）。我们计算出计算出我们的装置的RF=0.985以及RB=0.999。反射镜的吸收或衍射降低了反射率。因为典型DBR的反射带宽远大于（在我们的例子中，约100nm）放大器的带宽和空腔谐振波长λC，假定DBR中心波长相同，依赖DBR反射率的波长在这里忽略。我们的一维模型也忽略了横向的光学模式结构。在不同的横向模式中，共振波长略有不同。腔折射率nc，有效空腔长度Lc大于DBR距离LM，包括前后DBR的相渗透深度LF和LB，分别为(Lc=Lf+Lm+Lb)，无损DBR在中心波长λc的相渗透深度由下面给出当NC=3.2时，我们设备的DBR的穿透深度约为585nm。导致有效空腔长度lc=2.2μM。由于高指标对比，AlAs/GaAsDBR比以Inp为反射镜有较小的穿透深度。腔折射率Nc是通过两层DBR间所有层来求平均求得。通常情况下。在目标波长，它比衬垫材料的折射率高，但是它可以影响影响量子阱载流子密度以及装置的加热。剩余的需要研究的参数方程是单通道信号增益GS，假设横向均匀的材料性能达到信号点