超快光学 第19章 放大

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1、TheAmplificationofUltra-shortLaserPulsesFrancoisSalinCenterforIntenseLasersandApplications(CELIA)UniversitéBordeauxI,Francewww.celia.u-bordeaux.frsalin@celia.u-bordeaux..frGillesDarpentigny(CELIA),VincentBagnoud(LLE)AntoineCourjaud,ClemensHonninger,EricMottay(AmplitudeSystemes),LucVigroux(Amplitude

2、Technologies)andsomeadditionalstufffromDanMittleman,RicePulsecompressorttSolidstateamplifiertDispersivedelaylinetShortpulseoscillatorMostofthislecturecourtesyofPulseenergyvs.RepetitionrateReprate(pps)Pulseenergy(J)10910610310010-310-910-610010-3OscillatorCavity-dumpedoscillatorRegARegenRegen+multip

3、assRegen+multi-multi-pass1WaveragepowerAtWhatarethegoalsinultrashortpulseamplification?Ipeak=EIncreasetheenergy(E),Decreasetheduration(t),Decreasetheareaofthefocus(A).MaximumintensityontargetNeededtostarttheexperimentNeededtogetusefulresultsPave=ErSignalisproportionaltothenumberofphotonsonthedetec

4、torperintegrationtime.MaximumaveragepoweratthedetectorPulseenergyRepratePulseenergyBeamareaPulselengthIssuesinUltrafastAmplificationandTheirSolutionsPulselengthdiscrepancies:Multi-passamplifiersandregenerativeamplifiers(“Regens”).Damage:Chirped-PulseAmplification(CPA)Gainsaturation:Frantz-NodvickEq

5、uationGainnarrowing:BirefringentfiltersThermaleffects:coldandwavefrontcorrectionSatellitepulses,Contrast,andAmplifiedSpontaneousEmission:Pockels’cellsSystemscostlotsofmoney:Earnmoremoney…Pockelscellpolarizergainpumpinput/outputCavityDumpingBeforeweconsideramplification,recallthattheintracavitypulsee

6、nergyis~50timestheoutputpulseenergy.Sowehavemorepulseenergy.Howcanwegetatit?Whatifweinsteadusedtwohighreflectors,letthepulseenergybuildup,andthenswitchoutthepulse?ThisistheoppositeofQ-switching:itinvolvesswitchingfromminimumtomaximumloss,andit’scalled“CavityDumping.”E=ToutputEintracavityTransmission

7、ofoutputcoupler:~2%R=100%R=98%EintracavityECavitydumping:thePockelscellAPockelscellisadevicethatcanswitchapulse(inand)outofaresonator.It’susedinQ-switchesandcavitydumpers.Avoltage(afewkV)canturnacryst