laser1-研深圳大学-高等激光物理学期末复习课件

Part－1:LasersBasisUnit1IntroductiontolasersUnit2InteractionbetweenlightandmatterUnit3AmplificationoflightUnit4FromamplifierstooscillatorsUnit5OpticalpropertiesoflasersUnit6SpectraldistributionoflaseremissionUnit7PulsedlasersUnit8-9Diodelasers:semiconductorfundamentalsUnit10SemiconductordiodelasersUnit11Specificlasers#Unit1

IntroductiontoLasers

ApplicationsoflasersWhatissospecialaboutthelaser?BlackbodyDensityofmodesOpticalradiationandopticalmodesBlackbodyemissionspectrum#ApplicationsoflasersTelecommunicationsMedicineManufacturingMilitaryConsumergoodsBasicresearch#Whatissospecialaboutthelaser?

Highopticalpowerslasercanbefocussedtoverysmallspots

CollimationoftheopticalbeamThelightpropagateslargedistancesasa‘parallel’beamwithoutdivergingmuch.#

Monochromaticityorspectralpurity

Applications:spectroscopyandremotesensing.CoherentlightCoherenceisrelatedtothephasestabilityoftheelectro-magneticwaveThephaseofthewavesislockedtogetherforacertaindistance,calledthecoherencelength.#PulselengthVeryshortopticalpulses:10fsByrelyingonthepropertiesoflightwavesinaresonantcavity,itispossibletoproducelightpulsesthatareonlyabout10fslong.Extremelyshortlaserpulsesareusedtostudythedynamicsofatomicsystemsandnon-linearoptics.#BlackbodyAblackbodyisaperfectly‘black’object.Itisanobjectthatabsorbsallradiationthatfallsonit.Inthermalequilibrium,intheabsenceofthermalconductionandconvection,absorptionandemissionofenergyareexactlybalanced.Theradiationcomingfromablackbodyiscalledthermalorblackbodyradiation#Thermalradiationisnot(only)ofacademicinterest.ItexplainstheradiationfromtheSun,thelightbulbthemoderndigitalthermometersmeasurethetemperatureofthehumanbody.Ifweknowthenumberofmodes,wecancalculatetheshapeandmagnitudeoftheblackbodyemissioncurve.#BlackbodyDensityofmodesOne-dimensionalcavity.Thenumberofmodes:thedensityofmodes:#DensityofmodesAthree-dimensional(3D)cavityThedensityofmodesin3Das:#M.Planck,1858―1947,1900,1918Plancksuggestedhisnowfamoushypothesis:themode,atfrequency

,couldonlyhaveenergyinintegermultiplesofh.Foramodeoscillatingatafrequency

,theenergycouldonlybeE=0,h

,2h

,3h

,……..h＝6.63×10-34J·sEinstein，1905，E=h

，19211916，postulatesstimulatedemission

＃Planck’shypothesisPlanck’shypothesisE=0,h

,2h

,3h

,P(E)：theprobabilitythatthemodehasenergyEPlanckassumedthattheenergyinthemodesfollowedBoltzmannstatisticstheprobabilityP(E)ofaparticlehavingenergyEAverageenergypermode#EnergydensityoftheblackbodyDensityofmodes单位体积中，频率处于ν附近单位频率间隔内的模式数〔三维〕驻波条件→谐振腔模式密度〔《激光原理》P5〕Averageenergypermode①玻尔兹曼分布律〔热平衡状态下粒子按能量的分布规律〕②普朗克能量量子化假说→每个模式的平均能量〔《光学教程》P306〕Energydensityoftheblackbody单位体积中，频率处于ν附近单位频率间隔内的总能量即为“黑体辐射的单色能量密度”〔《激光原理》P10〕#Fig.1EnergydensityasafunctionofwavelengthofablackbodyradiatoraccordingtoPlanckandRayleigh-Jeans.BlackbodyemissionspectrumEnergydensityoftheblackbody

Planck’stheoryandtheexperimentalresultsareinexcellentagreement.

Energydensity～TEnergydensity～

ν#Unit1

IntroductiontoLaserscalculatemodesandmodedensitiesinone,twoandthreedimensionalcavitie