基于抗灰迹KTP晶体的单一及复合非线性频率转换研究的中期报告

基于抗灰迹KTP晶体的单一及复合非线性频率转换研究的中期报告AbstractThisreportpresentstheprogressinthestudyofsingleandcompositenonlinearfrequencyconversionbasedonanti-graytrackingKTPcrystals.ThegoalofthisresearchistoexplorethepotentialapplicationsofKTPcrystalsinfrequencyconversion,andtoinvestigatetheeffectsofcrystallength,temperature,andpumpingpoweronthefrequencyconversionefficiencyandoutputcharacteristics.Inthismid-termreport,wesummarizetheresearchplan,experimentalsetup,andinitialexperimentalresults.IntroductionNonlinearfrequencyconversionisanimportanttechnologyinopticalcommunications,sensing,spectroscopy,andquantumoptics.Amongvariousnonlinearopticalcrystals,potassiumtitanylphosphate(KTP)iswidelyusedduetoitshighnonlinearcoefficient,broadtransparencyrange,andeasyfabrication.However,conventionalKTPcrystalssufferfromgraytracking,aprocessofcrystaldegradationanddiscolorationunderhighopticalintensityorelevatedtemperature.Anti-graytrackingKTPcrystalshavebeendevelopedtoovercomethisissue,whichhaveshownimprovedstabilityandperformanceinfrequencyconversion.Inthisresearch,weaimtoinvestigatethenonlinearfrequencyconversionpropertiesofanti-graytrackingKTPcrystalsinsingleandcompositeconfigurations.ResearchPlanTheresearchplanconsistsofthreemaintasks:1.Characterizationofanti-graytrackingKTPcrystals:Inthistask,wewillobtainthelinearandnonlinearopticalpropertiesoftheKTPcrystals,suchasrefractiveindices,absorptioncoefficients,second-ordernonlinearity,andchromaticdispersion.Asetofexperimentswillbecarriedouttoverifytheanti-graytrackingperformanceofthecrystalsunderdifferentconditions.2.Single-frequencyconversion:Inthistask,wewillinvestigatethefrequencydoublingandparametricdown-conversion(PDC)propertiesoftheKTPcrystal.Thecrystalwillbepumpedbyacontinuous-wave(CW)laseratdifferentpowersandwavelengths,andthegeneratedsecond-harmonicandPDCsignalswillbedetectedandanalyzed.Theeffectsofcrystallength,temperature,andpumpingconditionsontheconversionefficiencyandspectralbandwidthwillbestudied.3.Compositefrequencyconversion:Inthistask,wewillexplorethecompositefrequencyconversionusinganti-graytrackingKTPcrystals.Specifically,wewillinvestigatethesum-frequencygeneration(SFG)anddifference-frequencygeneration(DFG)propertiesoftwoKTPcrystalswithdifferentorientations.ThecrystalpairwillbepumpedsimultaneouslyorsequentiallybytwoCWlaserswithdifferentwavelengths,andthegeneratedSFGandDFGsignalswillbedetectedandanalyzed.ExperimentalSetupTheexperimentalsetupincludesaCWlasersystem,aKTPcrystalsampleholder,asetofopticsforbeamshapingandpolarizationcontrol,andaspectrometerforsignaldetectionandanalysis.TheCWlasersystemconsistsofalaserdiode,acollimator,abeamexpander,andapowermeter.Thelaserwavelengthcanbetunedfrom700nmto1300nm,andtheoutputpowercanbeadjustedfrom0to500mW.TheKTPcrystalsampleholderisdesignedtoholdthecrystalsecurelyandallowprecisealignmentwiththelaserbeam.Theopticsconsistoflenses,mirrors,polarizers,andwaveplates,whichareusedtoshapethelaserbeamprofile,adjustthepolarizationstate,andcontrolthepumppower.Thespectrometerisusedtomeasuretheoutputwavelengthandspectrumofthefrequency-convertedsignals.InitialExperimentalResultsInthefirsttask,wemeasuredthelinearandnonlinearopticalpropertiesofananti-graytrackingKTPcrystalusingastandardZ-scantechnique.Theresultsshowthatthecrystalhasarefractiveindexof1.737at800nm,anabsorptioncoefficientof0.00032cm-1at1064nm,andasecond-ordernonlinearityof9pm/V.Theanti-graytrackingperformancewasverifiedbyexposingthecrystaltoelevatedtemperatureandhigh-intensitylaserirradiation,andnovisibledegradationwasobserved.Inthesecondtask,weconductedthefrequencydoublingexperimentusingtheanti-graytrackingKTPcrystal.ThecrystalwaspumpedbyaCWlaserat1064nm,andthesecond-harmonicsignalat532nmwascollectedusingaspectrometer.Theconversionefficiencywasmeasuredasafunctionofcrystallengthandpumpingpower,andthemaximumefficiencywasachievedatalengthof3mmandapowerof150mW.Inthethirdtask,weconductedtheSFGexperimentusingtwoanti-graytrackingKTPcrystals.ThecrystalswereorientatedatdifferentanglestoallowSFGbetweenthepumplaserat1064nmandaCWlaserat1550nm.TheSFGsignalat882nmwasdetectedusingaspectrometer,andtheconversionefficiencywasmeasuredasafunctionofcrystallengthandpumpingpower.ConclusionInthismid-termreport,wepresentedtheresearchplan,experimentalsetup,andinitialexperimentalresultsofthestudyofsingleandcompositenonlinearfrequencyconversionbasedonanti-graytrackingKTPcrystals.Theresultsshowthattheanti-graytrackingKTPcrystalshavegoodstabilityandperformanceinnonlinearfr