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Contents

7843: High-PowerLasersandApplicationsV . . . . . . . . . . . . . . . 2

7844: SemiconductorLasersandApplicationsIV . . . . . . . . . . . 19

7845: OpticsinHealthCareandBiomedicalOpticsIV . . . . . . . 30

7846: QuantumandNonlinearOptics . . . . . . . . . . . . . . . . . . . . . 54

7847: OptoelectronicDevicesandIntegrationIII . . . . . . . . . . . . 65

7848: Holography,DiffractiveOptics,andApplicationsIV . . . . 90

7849: OpticalDesignandTestingIV . . . . . . . . . . . . . . . . . . . . . 118

7850: OptoelectronicImagingandMultimediaTechnology . . 141

7851: InformationOpticsandOpticalDataStorage . . . . . . . . 164

7852: LEDandDisplayTechnologies . . . . . . . . . . . . . . . . . . . . 175

7853: AdvancedSensorSystemsandApplicationsIV . . . . . . 186

7854: Infrared,MillimeterWave,andTerahertzTechnologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

7855: OpticalMetrologyandInspectionforIndustrialApplications . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

1820October2010China National Convention Center

Beijing, China

AbstractSummaries

SPIE/COSPhotonicsAsia2010TechnicalProgram spie.org/pa ReturntoContents2

Conference7843:High-PowerLasersandApplicationsVMonday-Wednesday18-20October2010PartofProceedingsofSPIEVol.7843High-PowerLasersandApplicationsV7843-01, Session 1

NarrowlinewidthandwidelytunableoperationofTm:fiberlaserwithvolumeBragggratingsD.Shen,Y.Wang,W.Zhao,C.Li,K.Duan,XianInstituteofOpticsandPrecisionMechanics(China)

VolumeBragggratings(VBGs)recordedinphoto-thermalrefractive(PTR)glasscombinetheadvantagesofhighdiffractionefficiency(>99%),narrowspectralwidth(52Woutputpoweroveratuningrangeof104nmfrom1930to1826nm,whichis,tothebestofourknowledge,themostwidetuningrangedemonstratedtodateusingavolumeBragggrating.Over60.8Wofdiffractionlimited(M2~1.5)CWoutputpowerwasgeneratedat1930nmfor137Woflaunchedpumppower,correspondingtoaslopeefficiencywithrespecttolaunchedpumppowerof46%.Outputspectralwidths(FWHM)weremeasuredtobe


thenumericalmethod.Inthispaper,thehighslopeefficiencyhasbeenobtainedandoptimized.Besides,theslopeefficiencyisdecreasedby67%withtheincreasingoflaserreflectivityofoutputmirrorand22%withtheincreasingofpumppowerfillingfactorwhenthepumppoweris1000W,thedopingconcentrationis81026m-3andthecrossrelaxationcoefficientis110-22m-3s-1.Meanwhile,theslopeefficiencyincreaseswithincreasingthelaserreflectivityofinputmirror,thedopingconcentrationandthecrossrelaxationcoefficient,butthedopingconcentrationandthecrossrelaxationcoefficienthavemoreobviousinfluenceontheslopeefficientcomparedwiththelaserreflectivityofinputmirror.

7843-06, Session 2

Activeandpassivecoherentbeamcombiningofthulium-dopedfiberlasersP.Zhou,X.Wang,Y.Ma,K.Han,Z.Liu,NationalUniv.ofDefenseTechnology(China)

Recently,thulium-dopedfiberlaser(TFL),whichemittednear2umlaserbeam,hasbecomethelatestrevolutioninhigh-powerfiberlasertechnology.TFLcanfindwideapplicationinmedicine,lidar,materialsprocessing,andnonlinearfrequencyconversiontomid-infraredwavelengthregime.Nevertheless,furtherincreasingtheoutputpowerwillfacegreatchallengesinducedbynonlineareffectssuchasSBSandSRS.

Coherentbeamcombiningoflasersbeamscanincreaselaseroutputpowerwhilesimultaneouslymaintainingbeamquality.Severalapproacheshavebeenproposedandrobustcoherentcombiningofasmallnumberoffiberlasers/amplifiershavebeendemonstrated.AllthosedemonstrationfocusedonYb-dopedorEr-dopedfiberlasers.AstheincreasingrequirementofhighbrightnessTFLsismanyapplicationfields,coherentbeamcombiningofTFLisalsoakeytechnologydeservestobeinvestigated.

Inthismanuscript,wewillpresentourinvestigationoncoherentbeamcombiningofTFLs.Threedifferentapproaches,i.e.,interferometricarray,mutualinjectionlockingandactivephasingbasedonfrequency-ditheringtechnique,areemployed.

Intheinterferometricarrayscheme,coherentcombiningisrealizedbyusinganintracavityfibercouplerinanall-fiberlaserarrayconfiguration.Efficientcoherentcombiningcanbeachievedbyprovidingsufficientlossdiscrimination.Highcombiningefficiencyof85%fortwofiberlaserhasbeenobtained.

Inmutualinjectionlockingscheme,mutualcoherencebetweenthetwofiberlasersisestablishedbymeansofmutualcouplingthroughtwo3dBcouplers.Highcombiningefficiencyof99%fortwofiberlaserhasbeenobtained,andthefringecontrastoftheintensitypatternatthereceivingplaneisashighas93%.

Inactivephasingscheme,whenthephasecontrolsystemisintheclosedloop,thefringecontrastoffar-fieldintensitypatternisimprovedbymorethan90%from10%inopenloop,andtheresidualphaseerrorislessthan/15.

7843-07, Session 2

CoherentbeamcombiningofstimulatedBrillionscatteringbasedmultiwavelengthlasersX.Wang,P.Zhou,H.Chen,Y.Ma,X.Xu,Z.Liu,Y.Zhao,NationalUniv.ofDefenseTechnology(China)

Coherentbeamcombiningoffiberlasersisanefficientwaytogethighpowerlaserwithgoodbeamqualityasthefiberlaserpowerscalingisrestrictedintermsofthermalload,fiberdamageandnonlineareffect.Intwomainconfigurationofcoherentbeamcombining,including

passivephasingandactivephasingconfigurationmasteroscillatorpoweramplifier(MOPA)basedonactivephasecontrolisthemosteffectivewayforcoherentbeamcombining.InactivephasingMOPAconfiguration,signalfrequencyseedlaserisoftenconsideredtobenecessarytoimprovethespatialcoherencepropertyandobtainhighbrightnessinthefar-field.Nevertheless,theoutputpowerofthesinglefrequencyamplifierisabouthundredswattslevelasrestrictofnonlineareffects,especiallythestimulatedBrillouinscattering(SBS),andthisisagreatchallengetoincreasethetotalpowerofcoherentbeamcombining.Multi-wavelengthseedlasercansuppressSBSandimprovetheultimateoutputpowerofthefiberlaseramplifier.AccordingtoDajanietal,iftheamplifierseededbymulti-wavelengthwithwavelengthseparationisequaltoorgreaterthanthetwiceoftheBrillouinshift,theoutputpowercanbeaboutNtimesofasingle-wavelengthamplifieratSBSthresholdwithnosignsoffour-wavemixing.WhereNisthenumberoftheseedlaser.InthiswewilldemonstratecoherentbeamcombiningofstimulatedBrillouinscatteringbasedmultiwavelengthfiberlasersforthefirsttime.MultiwavelengthlaserisgeneratedusingstimulatedBrillouinscatteringbyseededa10kilometersinglemodefiberwithasinglefrequencylaser.Multiwavelengthlasersmorethan8wavelengthsaregeneratedandphaselockingofisachievedusingstochasticparallelgradientdescent(SPGD)algorithm.Themeanpowerofthemain-lobeinclose-loopis1.5timesofthatvalueinopen-loop.Asmultiwavelengthseededfiberamplifierscanreachahigherultimatepowersthansinglefrequencyseededamplifiers,thisarchitectureiseasilyscalabletohigherpowerwiththeMOPAconfiguration.

7843-08, Session 2

Mutualinjectionphase-lockedandcoherentcombinedofinter-relatedfiberlasersM.Zhu,Y.Chen,H.Wang,Y.Liu,C.Mi,C.Lu,WuhanMechanicalTechnologyCollege(China)

MutualInjectionPhase-Lockedcoherentlaserarrayseemstobeaimportantmethodforcoherentcombiningfiberlasers.Anovelfiberlaserisdesignedtorealizehighpowerandhighqualitybeamfiberlasercoherentbeamcombiningoutput.Thetwofiberlaserssharefiberbragggrating(R=0.85@1085nm)asprecedingmirror,sotheyareassociatedwitheachother.

Basedonacorner-cube,themutualinjectedenergyisenhanced.Andbyapolarizer,coherentbeamcombiningoutputisrealized.Throughexperiments:steadyinterferencestripeswithhighcontrastratio(about0.92)areobservedandabout9.4Woutputpowerisachievedwhichindicatesthatthepowercombiningefficiencyisapproximately90%,linewidthisalmost530GHz.Mutualinjection-lockingtheoryisanalyzed.

Thecombiningmethodcanbescaledtocombinemorelasers.Successfulattemptsofphase-lockedshowthatthismethodmayprovideapromisingwayinthefieldoffiberlasercoherent.

7843-09, Session 2

Thulium-dopedsilicafiberswithenhanced3H4levellifetime:modellingthedevicesfor800-820nmbandP.Peterka,I.Kasik,InstituteofPhotonicsandElectronicsoftheASCR,v.v.i.(CzechRepublic);A.Dhar,InstituteofPhotonicsandElectronicsoftheASCR,v.v.i.(CzechRepublic)andCentralGlassandCeramicResearchInstitute(India);B.Dussardier,W.Blanc,Univ.deNiceSophiaAntipolis(France)

Silica-basedthulium-dopedfiber(TDF)devicesoperatingaround810nmwouldextendthespectralrangecoveredbysingle-transversemode,high-powerfiberdevices.Thesedevicescanbeusedforfibersensors,instrumenttesting,healthcareandmedicineandfor

Conference7843:High-PowerLasersandApplicationsV


pumpingofspecialtypesoflasersandamplifiers.Particularly,bismuth-dopedfiberspumpedaround800nmmayshifttheirgainto1300nmtelecommunicationband,wherehighlyreliablesilica-basedfiberamplifiersarestillunavailable.BroadbandsourcesbasedonTDFswouldofferadvantagesofunpolarizedandhighpoweroutputthatareweakpointsofsuperluminescentdiodesusedinfibersensors.Ahigh-poweramplifierinthe800nmbandwouldbeusefulinshort-haulfree-spaceandopticalfibercommunications.

Usingacomprehensivenumericalmodelofthefiberwehaveshownthatefficientlasingat810nmcanbeachievedforspecificrangesofthelasercavityparametersandenhanced3H4lifetime.The3H4lifetimeof58swasmeasuredinourhighlyalumina-codopedfibersthatrepresentsasignificantimprovementcomparedtopureorweaklymodifiedsilicaglass(14s).Wehavepredictedmorethanthe30dBofgainoftheamplifierandmorethan500mWoutputpoweroftheASEsourcewithFWHMof5nmat3Wofpumppower.Twoupconversionpumpingschemesenablingcompactall-fibersetupareinvestigated:single-wavelengthpumpingataround1060nmanddual-wavelengthpumpingschemeat1455and1560nm.Dual-wavelengthpumpingschemewouldavoidpopulatingof1G4andhigherlevelsandcanmitigatethecolorcenterformation.

7843-10, Session 3

HighpowerhighstabilitygreenlaserbasedonLDpumpedcompositeceramicNd:YAGrodD.Xu,TianjinUniv.(China)

Wereporta153Waveragepowergreenlaseremployingintracavityfrequencydoublingofadiode-side-pumpeddoubleQ-switchedcompositeNd:YAGceramiclaser.Thetwosynchronizedacousto-opticmodulatorsareplacedorthogonallytoholdofftheveryhighpumpgainforefficientlyQ-switchingoperation.TypeIIhighgraytrackresistanceKTP(HGTRKTP)crystalisusedasdoublefrequencynonlinearcrystalinordertoavoidthegray-trackproblem.Thediode-to-greenopticalconversionefficiencyis14.27%.Tothebestofourknowledge,itisthehighestgreenpowerandefficiencyobtainedbyintracavityfrequencydoublingofthisnovelcompositeceramicNd:YAGlaser.Bothefficiencyandoutputpowerhavebeenimprovedgreatlycomparedtothepreviousreports.Themeasuredgreenlaserpulsewidthis162nswithrepetitionrateof25kHz.Thefluctuationmeasuredislessthan0.6%ataround150Waverageoutputpower.

7843-11, Session 3

MicrostructureandNIRtoVISupconversionluminescenceofY2O3:ErtranslucentceramicsD.Wang,Y.Guo,Q.Wang,Z.Chang,W.Zeng,JiujiangUniv.(China)

Y2O3:5%Ernanocrystallinepowderwaspreparedbylowtemperaturecombustionmethod.ThecrystalstructureandmorphologywereanalyzedbymeansofXRDandHRTEM.Theresultantpowdersweresinteredintotranslucentceramicsat1570degreeinvacuumfor6hours.ThemicrographofunpolishedsurfaceandfracturesurfacesshowedthatthesinteredY2O3:Erceramicswithaveragegrainsizeatabout10mhadhomogeneousmicro-structureandlowporevolume.Undertheexcitationof980nm,808nmand785nmdiodelaser,respectively,verystronggreenandredupconversionemissionsfromEr3+ionswereobserved,thepowerdependenceofupconversionemissionintensitywasmeasuredtodeducetheupconversionmechanism.Atrendofupconversionintensityincreasefirstandthendecreasewiththeexcitationtimewasalsofoundforthefirsttime.

7843-13, Session 3

Investigationofthermaleffectsinadiodeend-pumpedTm,Ho:YLFsolidstatelaserY.Peng,X.Zhang,L.Li,B.Jiang,HarbinEngineeringUniv.(China)

Thelaserdiode(LD)end-pumpedsolid-statelaserhasbeenalwaysinvestigatingrecentlyforitsadvantages,suchascompactandsimpleinstruction,highefficiency,stableperformanceandsoon.Thespectrumregionaround2mwhichcanbeemittedfromTm,Ho:YLFplaysanimportantroleinthefieldoflaserradar,remotesensingandhigh-resolutionmolecularspectroscopyforthegoodairtransmissionandeye-safety.TheinvestigationintheLDend-pumpedsolid-statelaserisfocusedonhowtoimprovetheoutputlaserpowerandoutputlaserefficiency.Butthermaleffectslimittheimprovementofthelaserperformanceandevenmaketheresonatorunstablebyreducingthepopulationoflaserupperlevelandchangingphysicalpropertiesofthecrystal.

Inthispaper,thermaleffectsareinvestigatedbynumericalandexperimentalmethods.ConsideringGaussianfielddistributionofpumplightandoutputlaser,asetof8-levelcontinuouswaverateequationsofTm,Ho:YLFlaserisgiven.Therateequationsaresolvedinthesteadystate,andthefractionalthermalloadingandthethermalfocallengthoftheTm,Ho:YLFlaseraretheoreticallyobtained.TheM2factorandthermalfocallengthasafunctionofthepumppoweraremeasuredbytheknifeedgemethod.M2factorsarelessthan1.2forvariouspumppowerswhichshowsthatthelaserbeamisTEM00mode.Thenthefocallengthasafunctionofpumppowerisobtainedbymeasuringthefar-fielddivergentangle,anditisfoundthatthetheoreticalresultsagreewellwiththeexperimentalresults.

7843-14, Session 3

StudyonsecondharmonicgenerationoutputinpulsedTEACO2laserR.Guo,D.Li,ChangchunInstituteofOptics,FineMechanicsandPhysics(China)

Firstly,throughthesecondmethodthecomparisonbetweentwononlinearcrystalsZnGeP2andAgGaSe2isconductedfortheirnonlinearcoefficientanddamagethresholdintheory.ThetheoreticalresultsshowthatthecrystalAgGaSe2ismoresuitablefortheSHGofpulsedTEACO2laser.WhenusingpulsedTEACO2laserwithwavelengthof9.3mtopumpingAgGaSe2SHGcrystal,thewavelengthof4.65misobtained.Intheconditionofrepetitionrate100Hz,theupmostoutputpowerofsinglepulseisuptolevelof1W,whichcorrespondingefficiencyofSHGisabout6%.TheexperimentalresultsshowthatthepolarizationoflaserbeamhasgreatlyinfluenceontheSHGoutputofthecrystal.Undertheradiationof3MW/cm2fromfundamentalwaveandtherightpositionformaximalSHGoutputinthecrystal,whenpolarizationoflaserbeamrotatesplus/minus4.5degree,theSHGoutputofenergydecreaseabout30%.Theresearchofthispaperwillmakeafoundationforfurtherdevelopmentofmid-infraredlaser.

7843-15, Session 3

EvolutionofshockwaveinTEAgaslaserC.Yang,D.Zuo,Z.Cheng,WuhanNationalLab.forOptoelectronics(China)andHuazhongUniv.ofScienceandTechnology(China);Y.Xu,WuhanNationalLab.forOptoelectronics(China);Y.Lu,WuhanNationalLab.forOptoelectronics(China)andHuazhongUniv.ofScience



andTechnology(China);L.Miao,WuhanNationalLab.forOptoelectronics(China)

Theevolutionofshockwavegeneratedbydischargeinthelaserchamberisoneofthekeyfactorswhichaffectlaserbeamquality,dischargestability,andrepetitionrateofTEAgaslaser.Inthispaper,Mach-Zehnderinterferometerisappliedtoobservethegasdensitydistributionevolutionafterdischarge.AndboththelongitudinalandtransversalshockwavesbetweenelectrodesaswellastheacousticwaveoriginatingfromthepreionizationinthedischargepumpingzoneofaTEAgaslaserareobservedbyusingtheshadowgraphmethod.AHe-Nelaserisusedastheparallellightsource,andallthephotographsimagedonthegroundglassarerecordedbyICCDcamera.Bychangingthedischargevoltage,gaspressureandgascomposition,thedevelopingprocessesindifferentconditionsarecomparedandanalyzed.Itisobservedthattheshockwaveoriginatingfromcathodeisdifferentfromtheanodesoneeveninthesymmetricconstruction.Andthewaveformandamplitudeoftheshockwaveareaffectedbythegascomposition,gaspressureanddischargevoltage.Furthermore,thegascompositionandpressurecanaffectthespeedofthewaveobviously.Inaddition,thetransversalshockismoreobviousthanthelongitudinalshockwave.Whatsmore,theshockwaveismoreobviousinhighCO2concentrationthanthehighN2concentrationandlessobviousinpureHegas.

7843-16, Session 3

OptimizationalgorithmforcompactslablasersC.Cao,XidianUniv.(China)

Anoveldesignofanefficient,highlyreliable,andgoodbeamqualitydiodeside-pumpedsolid-statelaserispresented.Efforthasbeendonetoobtainahighlyuniformpumpingintensityintheactivearea,whichsimultaneouslyreducestheeffectsofthermalgradient.Wereportacompact,conduction-cooled,highlyefficient,continuouswaveslablaserindiode-side-pumpedgeometry.Toachievehighefficiencyandnear-diffraction-limitedbeamquality,anovellaserheadhasbeendeveloped.Inaclose-coupledresonator,anovelpumpinggeometryisdemonstrated.

7843-17, Session 3

Mechanismanalysisandnumericalinvestigationofopticalbistabilityin2mTm,Ho:YLFsolidlaserB.Jiang,X.Zhang,L.Li,Y.Peng,HarbinEngineeringUniv.(China)

Aself-saturatedabsorptionmechanismisproposedtotheoreticallyinvestigatetheopticalbistabilityofTm,Ho:YLFlaser.Basedonthisbistabilitymechanism,therateequationmodelofthebistabilityisestablished.TheopticalbistabilitybehaviorsofTm,Ho:YLFlaserareobtainedbynumericalsimulating.Wealsoanalyzedtherelationbetweenlasergainandlosstoconfirmtherationalityofthebistabilitymechanism.Furthermore,thetimecharacteroftheopticalbistabilityisinvestigated.Itisfoundthatthepositivepulsepowerandthedurationofthepre-pumparetwomajorfactorsthataffectthelaserturn-ondelaytimeandtheirinfluencesontheturn-ondelayareanalyzed.

7843-18, Session 3

CoupledfiniteelementsimulationoflaserultrasonicW.Liao,D.Yang,NorthwesternPolytechnicalUniv.(China)

Thefiniteelementmodelsforlaserultrasonicinmetalfilmwerebuiltinthermoelasticandablationmechanism,respectively.Thegenerationandpropagationofultrasonicinacopperfoilirradiatedbyapulsedlaserwithnanosecondandsubnanoseconddurationsweresimulated.

Underthermoelasticcondition,weobtaintheoff-planedisplacementresultsoflongitudinalandshearwavebypulsedlaserwithdifferentbeamradius,intensityandpulsewidth.Itisconfirmedthatshortpulsegetsclearwaveformofultrasonic.

Forablationmodel,weuseanequivalentforceinsteadofthevaporpressureduringgasificationprocess.Theresultsshowthattheamplitudeofultrasonicinablationmodelisabouttenfoldtohundredfoldhigherthanthatinthermoelasticmodel.Thelongitudinalwaveandshearwaveiseasytoberesolvedinthedirectionof30thatdeflectedfromtheincidentpoint.Theultrasonicwaveformissharperwhilethesampleisclampedbetweenthesolidwindows.

7843-19, Session 3

EffectofvariableoxygenpartialpressureforSrTiO3thinfilmspreparationwithpulsedlaserdepositionX.Wan,L.Wang,J.Chen,X.Su,BeijingUniv.ofTechnology(China)

Inrecentyears,SrTiO3(STO)ferroelectricthinfilmhasgivenrisetomanyconcerns,andapulsedlaserdeposition(PLD)isoneofthemostwidelyusedandattractivedepositionmethodsforthegrowthofthinfilmsdeveloped.Italsoshowsanuniqueadvantageforthedepositionofferroelectricthinfilm.Inthispaper,STOthinfilmsonMgO(100)substrateweremanufacturedbyPLDusingthetriple-frequencyharmonicsofpulsedlaserNdYAG.ThethicknessoftheSTOthinfilmswasmeasuredusingastylusprofiler.TheirmicrostructureandsurfacemorphologywereanalyzedusingX-raydiffraction(XRD)andatomicforcemicroscopy(AFM).Additionally,theiropticalcharacterandelectricalcharacterwerecharacterizedusingopticaltransmissionspectrumandimpedanceanalyzer.Inaccordancewiththeabovetextresults,theoxygenpartialpressureisahighlyimportantparametertoinfluencethefilmmorphologyandfilmsgrown.ThesetasksthatwehavedonewillbringexperimentalresultstothefabricationofSTOthinfilmsforfurtherresearches.

7843-20, Session 4

Onenewqualityofthemaximum-likelihoodestimationoflaserpointingsystembyuseofreturnphotoncountsL.Zhou,InstituteofOpticsandElectronics(China)

Inalllaserpointingsystems,boresightandjitteraretwofundamentalpointingerrorsarisingfromvibrationsandatmosphericturbulence.Inordertoestimatetheseerrors,thepaperspresentedbeforehavedevelopedaseriesofestimators,whicharebasedonGaussianjittermodelanduseGaussianfar-fieldirradianceprofileandthestatisticsofreturnphotonsfromthetarget.Oneofthemismaximum-likelihoodestimation,whichcansimultaneouslyestimatejitterandboresightwithhighprecisionandspeediness.Besidesthesetraditionalqualities,anewqualityofthemaximum-likelihoodestimationisfoundinthispaperthattheestimatorhasdifferentperformancewithdifferentboresightand



jittererrors.Furthermore,bothMonteCarlosimulationsandexperimentalresultsdemonstratethatthemaximum-likelihoodestimationhasahigherdegreeofprecisionwhenboresightisbiggerthanjitter.Andthispapergivesacarefulanalysisofthenewqualityofthemaximum-likelihoodestimation.Inaddition,areasonabledeductionismadeafterafurtheranalysisoftheestimatormodelthatnotonlythemaximum-likelihoodestimationbutalsootherestimationhasthisnewquality.Inotherwords,theerrorsoflaserpointingsystemhadbetterbeestimatedwhenboresightisbiggerthanjitterorjitterisverysmall.Itwillbeveryusefulforthepeoplewhowishtoobtainhighpreciseresults.

7843-21, Session 4

Adaptiveinversecontrolofafaststeeringmirrorforelectro-opticalfinetrackingY.X.Xia,InstituteofOpticsandElectronics(China)

Faststeeringmirroristhemostimportantpartoftheelectro-opticalfinetrackingsystem.Atthebeginningofthispaperseveralreasonswhichaffecttheprecisionandbandwidthofthecontrolsystemwerediscussed.Comparedwiththegroundbasedplatform,theperformanceofthemovementbasedplatformelectro-opticalfinetrackingsystemwillbeaffectedbythemovementoftheplatform,moreover,thedisturbancesthatcausebeamjitterincludenarrowbandmechanicalvibrationsandbroadbandatmosphericdisturbances.So,alloftheserequirethecontrolsystemisawidebandwidthandarobustnesssystem.Anovelcontrollerforanelectro-opticalfinetrackingsystemisdesignedbasedonAdaptiveInverseControlprinciple.Theadaptiveinversecontrolisanadvancedalgorithm,theoretically,itcaneliminatedisturbancecompletely,moreover,itseparateprocessingtothesystemdynamiccharacteristicandtheobjectperturbationbutdoesnotaffectmutually.ComparedwiththePIDcontroller,thiscontrollerissimplerandtheparameterregulationismoreconvenient,butthecontroleffectisbetterandtherobustnessisstronger.TheexperimentincludestwoFSM,oneisusedasacontrollingFSMandtheotherisusedasadisturbanceFSM,thecontrollingFSMismountedonarotatingplatform,therotatingplatformsimulatingthemechanicalvibrations.ThesimulationandtheexperimentresultsindicatedthattheFSMcontrolsystembasedontheadaptiveinversecontrolalgorithmisveryeffective.Ithasahighperformanceonthetracingprecisionandthedisturbancesuppresses.Thusanewmethodisprovidedforthehigh-performanceelectro-opticalfinetrackingsystem.

7843-22, Session 4

Thespatialandtemporalevolutionofthebroadbandchirpedpulsewithsmall-scaleself-focusingY.Hou,X.Fu,H.Liu,L.Zhang,HunanUniv.(China)

Self-focusingisafundamentalphysicalphenomenoninnonlinearoptical.Inthedesignconsiderationsforsolid-statelaserfacilities,itismusttobepaidmorespecialattentiontothephenomenaofsmall-scaleself-focusing(SSSF)orfilamentation.ThebeamwillbecomemoreunstablewithhighopticalpowersbecauseofSSSFofthesmallphaseoramplitudemodulation,whichresultinginsplittingofthelaserbeam.Thisisanimportantfactorthatlimitstheusefulpowerofasolid-statelaser.Byexperimentsandsimulations,thespatialandtemporalevolutionsofthebroadbandchirpedpulsewithSSSFinnonlinearmediumhavebeeninvestigated.Firstly,westudiedthespatialmodulationgrowthofbroadbandpulsebyexperimentinCS2andthelaserwillproducemanysmallpeaksfromperturbationmodulation.Itisfoundthatmodulationgrowthofchirpedopticalpulsesisdelayedwiththepulsechirpincreasing.AndthenweinvestigatethetemporalevolutionofthepulseatthemodulationpeakandbottomduringtheSSSFbynumericalsimulation.Thenumericalsimulationisbasedonthespatial-temporalnonlinearSchrdingerequationandthesplit-

stepFouriermethod.Wefoundthatpulsewidthatmodulationpeakisdecreasingwiththeincreasingofmodulationpeakintensity.Butthepulseatmodulationpeakwillbroadenwhenthepeakintensityreachesthemaximumandthenthepulsebegantosplittingintotwoparts.However,thepulsewidthatmodulationbottomalwaysbroadenandfinallyreachtoaconstantvalue.Thesimulationresultsareinagreementwiththeexperimentalresults.

7843-23, Session 4

Controlofhighpowerlaserinnonlinearmediabylens-focusingandbeamself-focusingH.Liu,X.Fu,Y.Hou,J.Deng,HunanUniv.(China)

Manyofthescholarsdevotethemselvestoresearchthepropagationoflaserbeam.Theyconsideredthepropagationoflaserbeamwhichisaffectedbydiffraction,nonlineareffectsandotherphysicalaffects.Theappropriatefocalspotisusefulinuniformirradiationontargetplane.Buttheydidntpaymoreattentiontohowtocontrolthefocaldistanceandbeamqualityofhigh-powerlaseratfocusingspotinnonlinearmedia.Inthispaper,basedonthetheoryoflens-focusingandlaserself-focusinginnonlinearmedia,wefirstlypreliminaryanalyzedhowtocontrolthecollapsepositionofbeamwhenintensityandbeamwaisthavebeenvariedbythelaserself-focusinginnonlinearmediaandlens-focusing.Thechangingofbeamwaistbylensaffectsintensity,andthenthenonlinearpropagationwillbeaffectedbyintensityandnonlinearrefractiveindex.Weobtaintherelationsofthefocusingpositionwithinputpowerandfocallengthoflens.Thelengthoffocusingisinverselyproportionaltotheinputpoweranddirectlyproportionaltofocallengthoflens.Secondly,weinvestigatehowtocontrolthefocaldistanceandbeamqualityofhigh-powerlaseratfocusingspotinnonlinearmediabynonlinearpropagationequationandsplit-stepFouriermethod.Wedemonstratethatfocaldistanceshortenwiththeincreasingofinputpowerifwekeepbeamwaistandthefocallengthoflensunchanged,anditlengthenwiththeincreasingoffocallengthoflenswhentheinputpowerunchanged.Wecancontrolthefocusingspotatanypositionbychangedpowerandlens.Thenumericalsimulationsisgoodconsistentwiththeoreticalanalysis.

7843-24, Session 4

ThebeampropagationfactorofnonparaxialtruncatedHermite-GaussianbeamsZ.He,X.Kang,QiongzhouUniv.(China)

TheissueoftheM2factorusedforcharacterizingthelaserbeamqualitywithintheparaxialapproximationhasbeenwidelystudied.Insomepracticalapplications,whenthebeamwidthiscomparablewithorlessthanthewavelengthorwhenthefar-fielddivergenceanglebecomeslarge,theparaxialapproximationfails.Inrecentyearswiththerapiddevelopmentofmicrocavitiesandphotonicbandgapcrystalsetc.,thecharacterizationandpropagationofnonparaxialbeamsbecomemoreandmoreinteresting.Ontheotherhand,inpracticethebeampropagationissubjecttosomeextenttotheapertureeffect.Inthispaper,bytakingthenonparaxialHermite-Gaussian(H-G)beamdiffractedbyahard-edgedaperture,namely,thenonparaxialtruncatedH-Gbeamasanexample,theexpressionfortheM2factorofnonparaxialtruncatedH-Gbeamsisderivedandillustratedwithnumericalexamples.ItisshownthattheM2factorofnonparaxialtruncatedH-GbeamsdependsnotonlyonthetruncationparameterandbeamorderNbutalsoontheinitialwaist-widthtowavelengthratiow0/Thefar-fielddivergenceangleapproachesanasymptoticvaluewhenthetruncationparameter0.Furthermore,theM2factorsofnonparaxialtruncatedGaussianbeamsandnonparaxialuntruncatedH-Gbeamsaretreatedasthespecialcasesofourgeneralresult.



7843-25, Session 4

Adaptiveconversionofawavefront-distortionbeamtonear-diffraction-limitedflattopbeambasedonstochasticparallelgradientdescentalgorithmH.Ma,Z.Yu,X.Wang,Y.Ma,P.Zhou,X.Xu,Z.Liu,NationalUniv.ofDefenseTechnology(China)

Thetypicalintensitydistributionofthelaserbeamisoftenundesirableforpracticalapplications,especiallyforrequiringuniformintensitydistributionoverthecrosssectionofthebeam.Examplesincludemicromachining,laserwelding,isotopeseparation,laserprinting,opticalprocessing,laserradars,efficientpowerextractioninlaseramplifiers,andetc.Inmanylasersystems,wave-frontaberrations(WFAs)thatresultindeteriorationofbeamqualityarecommon.Thesewavefrontmayoriginatefromimperfectionsinthemanyopticalcomponents.Inthispaper,asystemofcontainingdualdeformablemirrors(DMs)isdesigned,whichcanefficientlyconvertawavefrontdistortionbeamtoanear-diffraction-limitedbeam.TheDMsarecontrolledbystochasticparallelgradientdescentalgorithm.ThefirstDMadaptivelyredistributestheintensityoftheinputbeamandtheotheradaptivelycompensatesthewavefrontoftheoutputbeam.ThewholesystemiscontrolledbySPGDalgorithm.Thecircleandsquareflattopbeamcanbeeasilyrealizedbythistechnique.Thedesignconsiderationisanalyzedindetail.Comparedwiththeconventionalbeamshapingsystem,suchasrefractive,reflectiveandresonatormodecontroller,thedynamicphasedistortionoftheinputbeamcanbecompensatedbythistechnique.Thetechnique,whicheliminatestherequirementofmeasuringtheintensityandphasedistributionsoftheinputbeam,canbeusedintheapplicationsofconversionofinputbeamwithvariousshapetooutputbeamwithvariousshape.Theintensitydistributionoftheoutputbeamcanbemaintainedforacertaindistanceinthenearfield.Thistechniqueprovidesanewmethodforgeneratingnear-diffraction-limitedflattopbeam.

7843-26, Session 4

OptimizationofapodizedBragggratingsforspectralbeamcombiningB.Shen,G.Zheng,J.Tan,Y.He,NationalUniv.ofDefenseTechnology(China)

Itisaneffectiveapproachtogethigh-powerlaseroutputbyspectralbeamcombining(SBC).VolumeBragggrating(VBG)recordedinPhoto-Thermo-Refractive(PTR)glassisthecommoncombiningelementsinSBC.ReflectingVBGusedatnear-normalincidenceismuchmoreadvantageousforhighdensitySBC.Buttheside-lobeofdiffractionefficiencyofreflectingVBGgreatlylimitsboththespectralseparationofcombiningbeamsandthenumberofwavelengthchannelinagivenspectralrange,whicharethecriticalparametersthatdeterminehighcombiningefficiencyandhighpowerlaseroutput,andalsotheside-lobecausesdiffractionlosses.Inordertosuppresstheside-lobeofdiffractionefficiency,inthispaper,aninnovativemethod-apodizedreflectionVBGforSBCisproposed.Wefirstanalyzeandcomparethespectraldiffractionefficiencywithdifferentapodizedprofiles(raise-cosine,sine,andquadratic-sine)usingChain-Matrixanalysis,andcalculatetheeffectsofindexmodulationamplitudeandgratingthicknessondiffractionefficiency.Then,westudytheimpactofvariousapodizedVBGontheperformanceofspectralbeamcombiningandmakeacomparison.TheresultsshowthatusingtheapodizedVBGgratings,theside-lobeofdiffractionefficiencyissuppressedverywell;thequadratic-sineapodizedprofileisthebestcandidateforsuppressingtheside-lobeofdiffractionefficiencybutitdecreasesthemaximumdiffractionefficiencyoftheVBGgrating;theraise-cosineapodizedprofiledoesnotcausemarkedlydiffractionefficiencydecreasingbuttheeffectsofside-lobeislargerthanquadratic-sine

apodizedprofileatthesameincidentconditionandgratingparameters.Takeintoaccounttheeffectsofgratingthickness,incidentbeamsspectralwidthandbeamdivergence,thecombiningefficiencybasedontheapodizedVBGisgiven.

7843-27, Session 4

DetectionofsulfurdioxideinairbylaserinducedbreakdownspectroscopyQ.Xu,X.Ma,H.Zhao,TsinghuaUniv.(China)

AstudyofthedetectionofgaseoussulfurdioxideinairbyLaserInducedBreakdownSpectroscopy(LIBS)isreported.Plasmaswereformedinthesulfurdioxidegas,andthreelinesofsulfurat560.61nm,567.77nmand565.99nmwereobserved.WefoundthatthemostappropriateexperimentalconditionsforLIBSdetectiononsulfurdioxidegasare:LaserPulseEnergy=100mJ,GateTimeDelay=2us.AfurtherstudywasmadeindetectingsulfurdioxidegasofdifferentconcentrationsbyLIBS.Finallywecalculatedthedetectionlimitofsulfurdioxidegasis330ppm.

7843-12, Poster Session

TheinfluenceoftheshapeofultrathinfoilsonthegenerationofattosecondpulsesbyfemtosecondpulsesJ.Zhu,Y.Song,L.Wang,P.Zhang,BeijingUniv.ofTechnology(China)

Thomsonscatteringoffersthepossibilitytogainthehigherfrequenciesofthescatteringelectomagneticwaves(wave)thanthat(ones)oftheincidentlight,whichopensanewwaytoproduceattosecondpulsescomparingwiththetraditionalmethodssuchashigh-orderharmonicgenerationinintenselaser-atominteractionsandself-amplifiedsponteneousemissionfromafreeelectronlaser.Furthermore,coherentThomsonscatteringmakesthewaymoreefficientwithradiatingelectromagneticpulseswithhigherenergydensity.

Inthispaper,weanalysedtheinfluenceoftheshapeoftheultra-thinfoilsdrivenbyfemtosecondpulsesonthegenerationofattosecondpulses.Intheseprocesses,therelativisticelectronlayers,whichproducedfromtheultra-thinfoilsforcoherentThomsonbackscattering,areusedforgeneratingattosecondpulses.Weinvestigatedthoroughlytheinfluenceaboveintheprocessesapplyingthemethodsofananalyticmodelandone-dimentionalpartical-in-cellsimulation(1D-PIC).Theresultsofthispaperarevaluablefordesigningattosecondpulsesinthefuture.


Highbeamquality400Wpracticalall-solid-statelaserforlaserbeamtextureA.Geng,C.Zhao,B.Li,BeijingTechnologyandBusinessUniv.(China)

Ahigh-average-powerandhigh-beam-qualitydiode-side-pumpedsolid-statelaserwasdesignedcarefullyforlaserbeamtexture.ByusingoflowconcentrationNd:YAGcrystalswiththermallynear-unstableresonatordesignandtwo-rodbirefringencecompensationtechnology,the1064nmcwoutputpowerof400Watpumppowerof1170WwasachievedwiththebeamqualityfactorM2~15,correspondingtoanoptical-to-opticalconversionefficiencyof34.2%.




AnalysisoflightpropagationinacirculardoublecladfiberusingcoupledmodemethodZ.Xu,NationalUniv.ofDefenseTechnology(China)andXianInstituteofOpticsandPrecisionMechanics(China);Z.Liu,NationalUniv.ofDefenseTechnology(China);K.Duan,W.Zhao,XianInstituteofOpticsandPrecisionMechanics(China)

Fibertechnologyhasattractedsignificantinterestduringthelastdecades.Theappearanceofdoublecladfibers(DCFs)providesanefficientwaytogeneratehighpowerfiberlaser.Incomparisonwithothertypesoffiber,DCFsbenefitfromtheirinnercladdingwhichresultsinalargeeffectivemodeareaandahighnumerical-aperture.Currently,lightpropagationinDCFshasbeentheoreticallystudiedbyusingthemethodsofraytracing,wave-opticalapproachandeigenmodeexpansion.Especiallyfortheeigenmodeexpansionmethod,thelightpropagationinaperfectcircularDCFisexplainedbythepropagationofacompletesetofguidedmodeandthefielddistributioninthecrosssectionareunchangedalongtheDCFs.

Inthispaper,insteadoftheeigenmodeexpansionmethod,weusethecoupledmodetheorytostudythelightpropagationintheperfectcircularDCF.Firstly,weuseanequivalentmodel:twocoupledfibers,i.e.,asinglemodefiber(SMF)andanannularcorefiber(ACF)toreplacetheDCF.WeobtaintheLP01mode(fundamentalmode)oftheSMFandtheguidedmodesoftheACFatdifferentwavelengthsbyusingweaklyguidingapproximation,andthencalculatethecouplingcoefficientsbetweentheLP01modeandtheseguidedmodes.Theresultsshowthatthemodesbetweenthetwofiberscanbestronglycoupledwhentheyhavethesamesymmetryandthecouplingcoefficientforthehigh-ordermodeoftheACFislargerthanthatforthelow-ordermode.WithconsideringalltheguidedmodesoftheACF,thefielddistributionsintheDCFscorearecalculatedatdifferentwavelengthsbyusingthecoupledmodeequations.Fromthecalculatedresultswefindthatthepowerinthecoreshowsaquasi-periodicdistributionalongtheDCF.TheaverageperiodofthedistributionincreaseswithincreasingwavelengthfordifferentDCFparameters,buttheaveragepowerinthecoreiscloselyrelatedtothechosenparametersoftheDCF.


Build-uptimeoftherandomlaserinR6GdyesolutionwithTiO2scattersS.Fan,X.Zhang,Q.Wang,Z.Chen,Z.Wang,R.Lan,ShandongUniv.(China)

Thedynamicpropertiesofthelaseremissionareveryimportantinstudyingthecharacteristicsofthelaserandmayrevealtheunderlyingoperatingmechanism.Randomlaserisanewlydevelopedtypeoflaserthatisimportantinthestudyofthephysicalmechanismofthelaser.Herewereportamoreprecisemeasurementofthebuild-uptimeofrandomlaserpumpedbypicosecondpulselaser.Thebuild-uptimeisdefinedasthetimedelayfromthepeakofthepumpingpulsetothatoftheemission.TherandomlaserisR6GdyesolutionswithnanometersizeTiO2asthescatterer.Variousdyeconcentrationsandscattererdensityaretriedandmeasured.Aspeciallycustomizedfiberandastreakcamerawithaspectrometerareemployedtomakethesimultaneousmeasurement.Thefiberhastwobranchesandthelengthsofbothbrancharemadeequal.Thedifferenceofthelengthsisprovedtobelessthan1mmintheexperiment.Thedispersionofthefiber,whichintroducesmucherrorintheresults,isalsomeasuredandlatercompensatedinthefollowingdataprocessing.Thestreakcamerawithspectrometercancatchtherandomlaserpulseandthepumpingpulsesignalinoneshotwitharesolutionoflessthan1picosecond.Theresultsforvarioussamplesaregivenandcompared,whichwillbeusefulinthestudyofthephysicalmechanismoftherandomlaser.


Broadlytunableytterbium-dopedphotoniccrystalfibrelaserandhighpowersuperfluorescentfibresourceB.Wang,S.Chen,CangZhouNormalUniv.(China);J.Wang,BeijingUniv.ofTechnology(China);Y.Li,NankaiUniv.(China)

Fibrelasershaveattractedmuchattentionespeciallyinrecentyears,foritsconvenienceofheatdissipationandsimplicitytoreachgoodbeamquality.Ytterbium-dopedfibreismostlypreferredinhighpowerfibrelasersforitssimpleenergylevelstructure,highconversionefficiency,andcommerciallyachievablelaserdiodepumpingsourcesat975nm.Byutilizingytterbium-dopedfibreasthegainmediumassociatedwiththecladpumpingtechnique[1],theoutputpowersoffibrelasersystemshaveexceeded1kW.

Inthispaper,Byutilizinganytterbium-dopedphotoniccrystalfibre(PCF)asthegainmedium,a2.5Wsuperfluorescentfibresource(SFS)andatunablePCFlaserwith74.4nmtuningrangeand5.5Woutputpowerareexperimentallydemonstrated.Thetunableoperationofthelaserisrealizedbyrotatingadiffractiongrating.Effectsofthedegreesofthecleavedangleattheanti-reflectionfibreendontheoutputcharacteristicsofthelaserandtheSFSareinvestigated.Alargecleavedangleisbeneficialtorealizeabroadlasertuningrangeandbeneficialtoobtainahighpowersuperfluorescentfibresourcewithoutparasiticlasing.


Supermodeanalysisinmulti-corephotoniccrystalfiberlaserY.Zheng,TianjinUniv.(China)andShijiazhuangUniv.ofEconomics(China);J.Yao,TianjinUniv.(China);L.Zhang,ShijiazhuangUniv.ofEconomics(China);Y.Wang,W.Wen,R.Zhou,Z.Di,TianjinUniv.(China)

Inrecentyears,muchattentionhasbeenpaidtofiberlasersbecauseoftheirabilitytoprovidehigh-powerandexcellentbeamqualitycomparedwithconventionallasersystems.However,thescalabilityofoutputpowerislimitedbymodeareaandnonlineareffectsinsingle-modefiberlaserandphotoniccrystalfiber(PCF)areintroducedtoovercometheselimitations.Themulti-corephotoniccrystalfiber(MPCF)laserisparticularlyinterestingbecauseitcansupportamorelargeeffectivemodeareaandmanytheoreticalandexperimentalresultshavebeenreported.Becauseofdistributednatureofthecores,thermomechanicaleffectscouldbemitigatedcomparedwiththoseofsingle-corelasers.BasedonthedesirablefeaturesoftheMPCFs,themulti-corephotonicfiberlaserwithin-phasesupermodesseemstobeanaturalwaytoscaleupthepoweroffiberlaserswhilekeepingtheirgoodbeamquality.

Inthispaper,wereportonthelaserpropertiesofmulti-corephotoniccrystalfiberlasers.Thesupermodeselectionofphotoniccrystalfiberswithlinearlyandcircularlydistributedmulti-coresisobserved.Thesupermodepropertiesareinvestigatedbyusingfull-vectorfinite-elementmethod(FEM).Themodeoperationsofour16-corerectangular-arrayand18-corecircular-arrayphotoniccrystalfiberlasersaresimulatedbytheCOMSOLMultiphysicssoftware.Thenear-fielddistributionandthefar-fielddiffractionpatternofin-phasemodearepresented.EffectivesupermodeselectionisobtainedbyusingtheTalboteffectandaperfectin-phasesupermodeisobtained.

SupportedbyNationalBasicResearchProgramofChinaunderGrantNo:2010CB327801andKeyProgramofNationalNaturalScienceFoundationofChinaunderGrantNo:60637010




NumericaloptimizationofYb-signalassistedhighpowerEr/Ybcodopeddouble-cladfiberamplifierQ.Han,J.Ning,W.Zhang,B.Chen,X.Wang,TianjinUniv.(China)

Co-seedinganEr/Ybcodopedfiberamplifier(EYDFA)withasignalintheemissionbandofYb3+hasbeenshowntobeapromisingwaytoimproveboththepowerconversionefficiency(PCE)andstabilityofhighpowerdouble-cladEYDFAs.InthispaperhighpowerEYDFAsassistedbyanYb-signalinthewavelengthrangefrom1000-1100nmarenumericallyinvestigated.TheresultsshowthattheselectionoftheYb-signalwavelengthandtheoptimizationofthefiberlengtharevitaltotheperformanceofanEYDFA.Asdemonstratedinthispaper,iftheseparametersareoptimized,PCEimprovementashighas>85%isevenpossible.However,iftheseparametersarechosenimproperly,theco-seedingofanYb-signalmaydetrimentaltotheperformanceoftheamplifier.OptimizedYb-signalassistedEYDFAprovidesasimplebuteffectivewaytoimprovetheavailablepowerinthe1.5umrangeforeye-safeapplications.


PulsedNd:YAGlasercuttingofsiliconwaferbycontrolledfracturetechniqueJ.Liu,J.Lu,X.Ni,G.Dai,L.Zhang,NanjingUniv.ofScienceandTechnology(China)

Thetraditionalmechanicalcuttingtechniqueforbrittlematerialswiththehelpofametalordiamondpointtoolhasbeenusedfordecades.Therefore,chipformationanduncertainfractureofthecutedgearetheintractableproblemsintheconventionalmechanicalcuttingprocessespeciallyforthinbrittlewafer.Controlledfracturetechniquehasgreatpotentialinlasercuttingbrittlematerials.Thistechniqueuseslesslaserpowerandenableshighcuttingspeedscomparedtootherlasercuttingmethods.Duringthelasercuttingofbrittlematerialusingcontrolledfracturetechnique,thermalstressisusedtoinducethecrackandthematerialisseparatedalongthemovingdirectionofthelaserbeam.InordertoinvestigatedtheprocessofpulsedNd:YAGlasercuttingbrittlesiliconwafer,athree-dimensionalmathematicalthermoelasticcalculationalmodelwhichcontainsapre-existingcrackwasestablishedinthispaper.Thetemperaturefieldandthermalstressfieldinthesiliconwaferwereobtainedbyusingthefiniteelementmethod.Duringthepulseduration,thechangesofstressintensityfactoraroundcracktipwereanalyzed.Thestressintensityfactorkeepsincreasingduringthelaserirradiationtime,whenitbecomeslargerthanthefracturetoughnessofthesilicon,thecrackextensionwilloccur.Meanwhilethemechanismofcrackpropagationwasinvestigatedbyanalyzingthedevelopmentofthetensilestressinducedatthecracktip.Themaximumtensilestressisalwaysatthecracktipbecauseoftheconcentrationofstressbythecrack,andthetensilestressatthecracktipkeepsincreasingduringthepulseduration.Whenthetensilestressinducedbythelaserbecomeslargeenough,thecrackwillpropagatealongthecuttingline.Thenextpulseduration,themaximumtensilestressisalsoinducedatthenewcracktipbecauseoftheconcentrationofstress,thecrackwillgoonpropagatebytheendoftheprocess.Thecalculationalresultsinthispaperareinagreementwiththereportedexperimentresults.


Studyonthesupermodeandin-phaselockinginmulticorefiberlasersY.Wang,J.Yao,Y.Zheng,W.Wen,R.Zhou,TianjinUniv.(China)

Multicorefiberlasershavelargermodeareas,resultinginhigherpowerthresholdsfornonlinearprocessessuchasstimulatedRamanscatteringandstimulatedBrillouinscattering.Becauseoflongerdistributeddistanceofthecores,thermalmechanicaleffectsaredecreasedcomparedwiththoseofsingle-corelasers.Therefore,multicorefiberlasersareproposedasacandidateforthepowerscaling.Theprogressofmulticorefiberlasersissimplyintroduced.Opticalfieldspropagatinginmulticorefibersarecoupledevanescently,resultinginwhatarecalledsupermodes.Inthisarticle,thecoupled-modetheoryforanalyzingsupermodeoffibertransmissionisintroduced.Bymeanofthetheory,assumingunderweak-couplingconditions,thesupermodesareapproximatedaslinearsuperpositionofmodesofindividualcoreswithappropriatecoefficients.Thenear-fieldandthefar-fieldmodedistributionsofthefundamentalin-phasesupermodearenumericallycalculated,andthecorrespondingmodedistributionpatternsaredrawn.Accordingtothemodedistributioninmulticorefiberlaser,thetransversesupermodecompetitionbetweensupermodesisdiscussedbasedonrateequationsextendedtofiberwithmultiplecores.

Formakingthemulticorefiberlaserpreferentiallyoperateinaparticularsupermodesothatimprovingbeamquality,anin-phaselockingmethodbasedonself-imagingTalbotexternalcavityispresented,andbyusingthemethod,aproperlyTalbotdistanceisgiven.TheresultshowsTalbotexternalcavitycanefficientlyachievein-phaselocking.


Apotentialapproachto~10fs,>2petawattpulsesbyhybridlaserbasedonTi:chrysoberylandTi:sapphireB.Cao,X.Lu,D.Fan,ShanghaiInstituteofOpticsandFineMechanics(China)

AhybridlasercomposedofTi:chrysoberylandTi:sapphireisproposedinthisletter.ThelaserhasthesimilarstructuretoordinaryTi:sapphirebasedlasersexceptthatthehostmaterialoftheregenerativeamplifierisreplacedbyTi:chrysoberyl.TheTi:chrysoberylisemployedinthissystemwiththepolarizationparalleltoaaxissincethenitsphotoluminescencespectrumhastwopeaks.Asimplifiedtheoreticalmodelfornumericalsimulationispresentedhere.Theabilityofthehybridamplifierchaintocompensatethegainnarrowingisobviouslydemonstratedandthelaserispotentialtogenerate~10fs,>2petawattpulsesaccordingtothenumericalsimulation.


DetectionofsurfacebreakingoncylindermaterialusingsurfaceacousticwavegeneratedbyscanninglasersourceY.Shi,L.Zhang,L.Cai,ChinaAero-PolytechnologyEstablishment(China)

Laserultrasonics,anondestructivetestmethod(NDT),ismoreandmoreappliedinindustrialfieldssuchascrackdetectioninmetalandnonmetallicmaterials,andsizemeasurementandweldedjointexamination.Accordingtothethermoelastictheory,afiniteelementmodelforlaser-generatedsurfacewavesontheelasticcylindermaterialisbuiltandanexperimentalinstallationusinglaserinterferometerastheultrasonicwavereceiverissetuptoverifythenumericalresults.



Bychangingtherelativedistancebetweenthelasersourceandthesurfacenotchinthecomputation,thescanningprocedureissimulated.Thecorrespondingvarietiesofamplitudesofthesurfacewaves,whichpropagatecircumferentiallyonthecylindermaterial,arepresentedandthephysicalmechanismsareanalyzed.Theinfluenceofthedepthofthesurfacenotchisalsodiscussed.TheresultsdemonstratetheSLStechniquecanbeappliedtodetecttinycrackwhosedepthissmallerthanthewavelengthoftheSAW.


Optical-mechatronicshighpeakpowerultrashortpulseUVlasersystemJ.Chen,Chung-HuaUniv.(Taiwan)

WehavedevelopedanOptical-Mechatronicshighpeakpowerultra-shortpulseUVlasersystem.Thismulti-functionaldiversifiedUVlasersystemhavsmanysub-systemsthatcanbeemployseparately.Itcanbeatunablefemto-secondlaserseedsource,mediumpowerultra-shortpulseslasersystem,singleamplifiedmediumpowerultra-shortpulselasersystem,multi-frequenciessingleamplifiedmediumpowerultra-shortpulselasersystem,mediumpowerultra-shortpulsesUVlasersystem,andconcludingthehighpeakpowerultra-shortpulseUVlasersystem.Thecompletelasersystemlayouttogetherwithsynchronizationcontrolsofallthelasersystemwillbepresentindetail.


FemtosecondopticalparametricoscillatorbasedonperiodicallypoledpotassiumtitaniumphosphateX.Ma,J.Tian,X.Zhang,BeijingUniv.ofTechnology(China)

Wedescribeasynchronously-pumpedopticalparametricoscillator(OPO)basedonperiodicallypoledpotassiumtitaniumphosphate(PPKTP).TheOPOwaspumpedbyaself-mode-lockedTi:sapphirelaser.Itssignalwavecoversfrom1070nmto1375nm,andcouldbetunedfreelybycavity-lengthtuning,thecorrespondingidlerwavecoveringfrom1.9umto3.2uminthemid-infraredregion,andthered,greenandbluevisiblelightwasalsogeneratedbyintra-cavitysumfrequencyandfrequencydoubling.Thethresholdwasmeasuredtobeabout250mWat810nmpump.Athinglasssubstratewasinsertedtothecavityforoutputcoupling,andthemaximaloutputpowerwasmeasuredtobe26mW.Weadoptedringcavityandlinearcavityexperimentally.AfteroptimizingtheOPOsoperationparameters,theoutputcharacteristicsoftheringcavityandlinearcavitywereinvestigatedrespectively.Theapproachtoimprovetheoutputefficiencywasalsodiscussed.


Signal-to-noiseratioofairbornelidarsystemH.Hao,BeijingInstituteofTechnology(China)

Abstract:Laserlightdetectionandranging(Lidar)systemisausefultoolforrangedeterminationinvariousapplications,particularlyifitprovidescompactandrobustset-upswithsuitablelightsource,efficientsensorsandadequatesignalprocessing.ThisarticlegivesanoverviewofairborneLidarsystemanditsapplication.Byanalyzingthetransmissionandreceptionprocessoflasersignal,thearticleconstructsamodelofbackscattersignaloftheLidarsystem,andgivessomebasicformulaswhichmakeuptherelationshipofsignal-to-noiseratio,forexample,thereceivedpower,thedarknoisepowerandsoon.Andthisarticlecarefullystudiesandanalyzestheimpactofsomeimportantparametersintheequationonthesignal-to-noiseratio,suchastheatmospheric

transmittancecoefficient,theworkdistance.Andthematlabsoftwareisusedtosimulatethedetectionenvironment,andobtainsaseriesvaluesofsignal-to-noise(SNR)ratiounderdifferentcircumstancessuchassunnyday,cloudyday,day,night.AndthefigureswhichdescribehowtheSNRofLidarsystemisinfluencedbythecriticalfactorsareshowedinthearticle.Finallyaccordingtotheseriesvaluesofsignal-to-noiseratioandthefigures,theSNRofLidarsystemdecreasesasthedistanceincreases,andtheatmospherictransmittancecoefficientcausedbybadweatherdecreases,andalsohighworktemperaturedropstheSNR.Dependingontheseconclusions,theLidarsystemwillworkevenbetter.


NonlinearimagesofgaindefectsY.Hu,H.Wu,Q.Zheng,J.Xu,HunanUniv.ofScienceandTechnology(China)

Thenonlinearimageofopticaldefectisathreatforthesaferunningofhigh-powersolid-statelasersystems.Thenonlinearimageeffectforsmall-scalescattererswithgaindefect,whichmaybecausedbytheunevengainingainmedia,isinvestigatedbynumericallysolvingthepropagationwiththestandardsplit-stepfast-Fourier-transformalgorithm.Twocases,i.e.thescatterersonlycaussinggainandthescattererscausinggainandphasemodulationsimultaneously,aremainlyconsidered.Itisprovedthatnonlinearimagescanalsobeformedforscattererswithgain.However,whencomparedtothenonlinearimageeffectforscattererswithattenuation,thefollowingsignificantdifferencesarefound:firstly,theintensityatthepointcorrespondingtothecenterofthescattererexperiencesanobviousdecreasingjustbeforethenonlinearimageisformed,contrarytothecasethatthescattererwithoutgain;secondly,thisdecreasingisenhancedasthescatterersgainincreases;thirdly,thereisadistanceseveralcentimenters,evenmorethantencentimeters,betweenthenonlinearimagesofscattererswithgainandthosewithattenuation.Forscattererswhichcausegainandphasemodulation,abovedifferencesareignorable,butthenonlinearimageeffecthassomenewproperties:firstly,thepeakbeamintensityontheexitsurfaceofthenonliearmediumishigherthanthecasethescattererwithphasemodulationonly;secondly,thesecond-ordernonlinearimageisincreasedobviously,buttheeffectofthescatterersgainontheimagespeakintensityisrelativelylimited.Besides,theeffectofthedistancebetweenthescattererandthenonlinearimageandthatofthepoweroftheincidentbeamarediscussed.


Highpowerwidelytunableallsolidstatepulsedtitanium-dopedsapphirelaserQ.Sheng,X.Ding,J.Yao,N.Chen,B.Li,TianjinUniv.(China);X.Yu,NankaiUniv.(China);X.Li,W.Wen,R.Zhou,TianjinUniv.(China)

Wereportapulsed,widelytunableTi:sapphirelaserpumpedbyanall-solid-stateQ-switchedintra-cavityfrequency-doubledNd:YAGlaser.Torealizehighconversionefficiency,thelasercavitywasdesignedforwellmodematchingbetween532nmpumpbeamandTi:sapphirelaserbeaminthesapphirecrystalbasedonmeasuredthermalfocallengthoftheTi:sapphirecrystal.The220mmflat-flatcavityand195mmthermalfocallengthatthemaximumpumppowerbroughta220mTEM00modespotradiusof780nmTi:sapphirelaserbeam,whenthepumpbeamradiuswasfocusedto200mintheTi:sapphirecrystal.Meanwhile,theTi:sapphirelaserwasalsooperatingatthestable-powerpointofU-shapedcurveindicatingchangeofspotradiusversusthermallensfocalpower.

Usingtwodenseflintglassprismsasdispersionelements,theoutputcouldbecontinuouslytunedover675-970nm,withspectrallinewidthoflessthan2nm.Duetogain-switchedcharacteristicsofTi:sapphire



laser,thepulsewidthcanbeasshortas17.6ns.Attheoptimizedrepetitionrateof7KHz,themaximumoutputpowerwas6.2Wat780nmwhenthe532nmpumppowerwas22W,withlaserthresholdof8.2W;correspondingconversionefficiencywas28.2%.


AnewfluidstatelasersystemrealizeslaseroutputL.Gui,ShanghaiInstituteofOpticsandFineMechanics(China)

Thisarticledemonstratesadiode-pumpedpulselaseroperationinaflowingfluidhostcontainingNd-glassparticles,transverselypumpedby810nmlaserdiodes.AseriesofLaserpulseastheoutputareobserved.Therepetitionfrequencyis1Hz,andthepulsewidthisabout100,andthepeakpulseenergyisupto2.93mJ,andtheaveragepulseenergyis0.84mJ.Giventhatfluidcirculationoffersimprovedheatmanagement,therealizationoflaseroutputofthisnewfluidstatelaserverifiesapracticalwaytosolvetheheat-inducedproblemsinhighenergylasersystems.


FiberlaserintensitynoisesuppressionthroughoptoelectronicfeedbackF.Zhang,J.Zhu,Y.Ke,L.Jing,X.Shi,C.Li,B.Yu,AnhuiUniv.(China)

Inthispaper,wedemonstrateatechniqueforsuppressingtheintensitynoiseoftheerbiumdopedfiberlasers(EDFL)atlowfrequency(about10KHz).Weshowthatbyusingnegativefeedbackintothepumpdrive,therelaxationoscillationnoisecouldbesuppressed.andwealsothroughnegativefeedbackintotheLiNbO3intensitymodulatorwhichinsertedintothecavity.Comparedwithpreviousnegativefeedbackmethodsofsuppressingtheintensitynoise.Inordertosuppressiontheintensitynoiseatlowfrequencyandpreventtherelaxationoscillationfrequencymovetothehigherfrequency,webothfeedbackintothecavityandthepumpdrive.


OpticalfrequencycombgenerationbasedonstimulatedBrillouinscatteringinhighlynonlinearfibersX.Zhang,Z.Cao,F.Ai,B.Yu,AnhuiUniv.(China)

Inthispaper,asimpleandall-fiberfrequencycombgeneratorbystimulatedBrillouinscattering(SBS)inhighlynonlinearfiber(HNLF)isdemonstrated.Theopticalresonatoriscomposedofasegmentofhighlynonlinearfiberandtwoopticalloopmirrors.Atunablelaserisusedasthepump.Whenthewavelengthandthepowerofpumplaserareadjustedcorrectly,dozensofcomblineswithcombspacinginthe10GHzrangeareobtained,whileaseriesoflongitudinalmodesspacingin100kHzarealsoappeared.Besidesthese,anerbium-dopedfiberamplifier(EDFA)andapolarizationcontrollerwillbeusedtoamplifythepowerofpumpandadjustthepolarizationstateofthelightintheresonatorrespectively.Itcanbeexpectedthatmorecomblineswouldbeachieved.


Modecompetitioninconcentric-typemulticorefiberlaserscombinedwithlargemodeareasinglemodefiberX.Zhang,ShandongUniv.(China);G.Peng,TheUniv.ofNewSouthWales(Australia);X.Zhang,J.Chang,Q.Wang,P.Li,S.Zhang,ShandongUniv.(China)

Themodecompetitionmechanisminconcentric4-coreand7-corefiberlaserswithlargemodeareasinglemode(SM)fiberasin-phasesupermodeselectioncomponentispresented.ThecouplingcoefficientbetweenthefundamentalmodeinlargemodeareaSMfiberandeachsupermodeinmutlicorefiberisdiscussed.Forindividualsupermodeinmulticorefiber,thecouplingcoefficientisoptimizedasafunctionofthecoreradiusofSMfiberaswellasthedistancebetweenmulticorefiberandSMfiber.Theoptimizationresultsdemonstratethatonlytwosupermodesareinvolvedinconcentric-typefiberlasing-in-phaseandanti-phasesupermode,owingtothenegligiblecouplingcoefficientsoftheothersupermodes.Furthermore,toachievethebestin-phasesupermodeselection,thecoreradiusofSMfiberwillbeoptimizedformaximumcouplingcoefficientdifferencebetweenin-phasesupermodeandanti-phasesupermodes.Inthiscase,theanti-phasemodeseemsnoncompetitiveregardlessofthedistance.Thenumericalresultsillustratethatin-phasesupermodealwaysdominatetheoutputandishighestcompetitivewhenthedistanceequalszero.ComparedtoconventionalmulticorefiberlaserswithTalbotcavity,thisall-fiberconfigurationbasedonlargemodeareaSMfiberhashigher-ordersupermodesmoreefficientlysuppressed,consequentlyhigh-brightnessoutputisobtained.


EffectofprocessparametersonthegrowthofdendriteinlasercladbeadQ.Li,HunanUniv.(China)

LasercladdingwasperformedonthesurfaceofductilecastironsubstratewithFe-baseallayunderdifferentprocessparameters.ThemicrostructureofcladdinglayerwasanalyzedusingSEMandMetallurgicalMicroscope.Thesecondarydendritearmspacingwasmeasured.Theresultsshowedthat,withinacertainrangeoflaserenergydensity,withincreaseintheenergydensity,thesecondarydendritearmspacingaswellasthesizeofthegrainrises.Themicrohardnessofthecladdinglayerbecomeslowerandlower.


LasersurfacehardeningofductilecastironforvehicledieY.Xu,HunanUniv.(China)

High-powerlasertransformationhardeningimprovesthesurfacepropertiesofmetallicmaterials.Lasersurfacehardeningtreatmenthasmanyadvantagesoverconventionalhardeningtreatments,suchasoutstandingwearresistance,highfatiguestrength,smalldimensionaldeviationandsoon,thusitisdevelopedformanyindustrialapplicationsinrecentyears.Ductilecastiron,whichispopularinindustry,especiallyinautomobileindustry,areoftenusedaftersurfacetreatments.Inthispaper,lasertransformationhardeningiscarriedoutontheductilecastironblocksbyusingcircularCO2laserbeamwithvariationsinlaserpower,spotsizeandscanningspeed.Differentpatternsofthelaserscanpathisalsostudied,includingasingle-passhardeningpattern,amulti-passhardeningpatternwithoverlappingandthatwithoutoverlapping.Thedistributionofmicrohardnessalongcrossand



longitudinaldirectionsandthevariationofmicrostructureofhardenedlayerareinvestigated.Itisseenthatthesurfacehardnessofductilecastironblocksincreasesgreatlyatsuitablevaluesofprocessparametersinlasertransformationhardening,whichsatisfiestheautomotivedieswithanincreaseinservicelife.


Beamcleanupofa5mJ-200spulsedgreensolidstatelaserusingabimorphmirrorX.Lei,N.Yu,P.Yang,L.Dong,W.Liu,Y.Hu,B.Xu,InstituteofOpticsandElectronics(China)

Itiswellknownthatinapplicationsofthepulsedsolid-statelaser,highbeamqualityisoneofthemostimportantorientationsforphysicists.However,thewave-frontdistortionswithinthelaserscauseithardtorealize.Thereareseveralsourcesofwave-frontdistortionsinapulsedsolid-statelaser,forinstance,thenon-lineareffectsofmaterials,thermallensingetc.Allcontributetothedegradationofthebeamquality.Togethighbeamqualitybybeamcleanup,scientistshavedevelopedmanyways.Insuchmethods,adaptiveoptics(AO)systemsusingdeformablemirrorshavebeenappliedforlaserbeamcleanupandprovedtobeeffective.

ConventionalAOsystemsusedforlaserbeamcleanupmainlyincludethreeparts:awave-frontsensor(WFS,mostofthemareHartmann-Shacksensors),anactivecorrectionelementandacontrolstrategy.WhentheseAOsystemsareappliedtocorrectwave-frontaberrations,firstly,theaberrationsaremeasuredbytheWFSdirectly.Then,basedonthewave-frontinformation,thewave-frontaberrationsarecompensated.Howeverinthestrongscintillationregimeorwhentheintensityoflaserbeamisrathernon-uniform,conventionalAOsystemsbasedongradientwave-frontsensorsmaynotobtainverygoodresults.Togetanalternative,optimization-basedAOcontrolsystemshavebeendevelopedforimprovinglaserbeamquality.Inthispaper,wepresentanAOsystemforbeamcleanupofapulsedsolid-statelaserwhosewavelengthis532nm.Therepetitionrateofthispulsedlaseris20Hzand100Hz.TheAOsystemiswave-frontsensor-lesswhichisbasedonStochasticParallelGradientDescent(SPGD)algorithmanda20-elementbimorphmirror(BMforshort).Theresultsarepresentedanddiscussed.


FresneldiffractionbycircularapertureilluminatedwithaphasemodulatedandspectraldispersedlaserbeamsJ.Deng,X.Fu,L.Zhang,Z.Jin,S.Wen,HunanUniv.(China)

Uniformilluminationontargetplaneandafocalpatternwithsharp-edgeandflat-topprofileisessentialinthedirect-driveapproachtoinertialconfinementfusion(ICF).Anumberofbeamssmoothingmethodshavebeensuggestedtoimprovelaserirradiationuniformityonthetargetplane.Smoothingbyspectraldispersion(SSD)isatemporalsmoothingtechniquethatissuitableforglasslasersystem(e.g.OMEGAlaserinUniversityofRochester),andhaveproventhatSSDcaneffectivesmooththehigh-frequencyintensitymodulationinthetargetplane.Inpractice,SSDdeviceisusuallylocatedbeforethemainamplifier,whichmeansthatthebeamsphasemodulatedandspectrallydispersedbytheSSDdevicewillbetransmittedthroughtheentireamplifiersystem.However,almostallresearchofSSDconcentratedonthefocalspotsmoothing,andobviouslySSDinstallationalsowillsignificantlychangethenear-fielddiffractioncharacteristicsofthebeamsaftertheSSDdevice.Inthispaper,theFresneldiffractioncharacteristicsofaphasemodulatedandspectraldispersedbeam(thebeamafterSSDdevice,termedPM-SDbeam)whichpassedacircularapertureisinvestigateddetailusingnumericalsimulation.WecomparedthediffractionpatternsofPM-SDbeamandmonochromaticbeamilluminations,andfound

thatPM-SDbeamcansignificantlychangethedistributionofthenear-fielddiffractionintensity.WealsodiscussedtheeffectsofthemainparametersoftheSSDinstallationsuchasfrequencyandamplitudeoftheelectro-opticmodulatorandcoefficientofthegratingdispersion,andfoundthatwhenchoosingappropriateparameters,wecanobtainasmoothingnear-fielddiffractionpattern.ThisimpliesthatPM-SDbeamcanreducethesourceofsmall-scalefocusing,becausethespatialintensitymodulationgeneratedbydiffractionandinterferenceisthemainreasonofspatialsmall-scalefocusing.


OptimumdesignofDBREr/Ybco-dopeddoublecladdingfiberlaserH.Su,Y.Geng,Z.Guan,Q.Guo,HebeiUniv.(China)

Er3+/Yb3+co-dopeddoublecladdingfiberlasers(EY-DCFL),asakindofhighefficiencyandhighpowerlevellasersourceoperatingintheeye-safewavelengthregionaround1.55m,havebeenpaidgreatattentionanddevelopedrapidlyinrecentyears.DistributedBraggreflection(DBR)configurationwhichusesfiberBragggratings(FBG)asthereflectortoformtheresonatorhasbeenappliedinEY-DCFLforthesakeofcompactnessandwavelengthstability.TooptimizetheperformanceofDBREY-DCFL,inthisworktheoutputcharacteristicsofDBREY-DCFLswithdifferentparametersareinvestigatedtheoreticallyandexperimentally.NumericalsimulationontheoutputcharacteristicsofDBREY-DCFLisperformedbasedonrateequationsandpowerpropagationequationsoftheEr3+/Yb3+co-dopedsystem.Theoutputpowersasfunctionsofthelaunchedpumppower,thegainfiberlength,thereflectivityoftheoutputmirror,aswellastheconcentrationoftherare-earthionsinthefiberarepresented.Comparativeexperimentalstudyontheoutputpower,spectralpropertiesandtime-domainstabilityofDBREY-DCFLsformedbyfiberBragggratingswithdifferentreflectivityarecarriedout.Intheoptimumcondition,themaximumoutputpowerofthefiberlaseris2Wwithaslope-efficiencyof53.8%,andthelasingcenterwavelengthand3dBbandwidthare1550.8nmandabout0.02nm,respectively.Theexperimentresultsdemonstratethecorrectnessofthetheoreticalstudy.


AnefficientalgorithmbasedonpropagationequationsofTm-dopeddouble-cladfiberlaserJ.Liu,C.Zhao,X.Fu,S.Wen,HunanUniv.(China)

Inthetheoreticalanalysisofdouble-cladfiberlasers,theyareanalyzedusingthenumericalalgorithmoftwo-pointboundaryvalueproblems.Amongthesealgorithms,theshootingiscommonlyused.Buttheinputpumppowerisknown,theboundaryconditionsoflaserpowerareonlygiveninthedouble-cladfiberlaser,andtheiterationprogressoftheinitiallaserpowerisquitecomplex.So,theshootingalgorithmfordouble-cladfiberlaserisrelativelycomplicated.Inthispaper,anefficient,simpleandfastalgorithmbasedonthepropagationequationsofTm-dopeddouble-cladfiberlaserisproposed,inwhichtheinitialguessedvalueisdirectlycorrectedbasedontherelationofthetwo-endboundaryvaluesoflaserpower,anditisnotnecessarytoknowtheinitialorterminallaserpower.Then,theevolutionsofthepumpandlaserpowersalongthefiberareanalyzed.Itisprovedthattheinitialguessedlaserpowercanbefastconvergenttothetruthvalueregardlessofthemagnitudeoftheinitialguessedlaserpower,andthisalgorithmcanbeeffectiveevenifthepumppowerisuptokilowattlevel.Finally,comparedwiththeshootingalgorithm,theiterationprogressofthisalgorithmiseasier,andtherunningtimeis17timesasfastasthatoftheshootingalgorithm,sothisalgorithmcanbemorequicklyandsimplerconvergenttothetruthvalue.So,thisalgorithmcanbeusedintheTm-dopeddouble-cladfiberlaserefficiently.




Effectsofthegasflowandthedefocusingdistancefromlaserbeamfocusonpowder-feedlasercladdingY.Li,HunanUniv.(China)

Inthispaper,theeffectsofthegasflowanddefocusingdistancefromlaserbeamfocusonpowder-feedlasercladdingareinvestigated,andanumericalmodeltosimulatethefreesurfaceofthemoltenpoolisdeveloped.Theeffectoftransportinggasflowonthepowderfeedrate,andthoseofthetransportingandshieldinggasflowonthedivergentangleofthegas-powderflowandthecharacteristicsoftheformedcladbead(height,width,surfacesmoothness,poreandcrack)areworkedout,respectively,whiletheotherprocessvariablesbeingconstant.Suitablevaluesofthetransportinggasflowandshieldinggasflowcanbeobtainedfromtheexperiments.Providedthatthereisnoheatexchangeinpowder-gasflow,theequationsofmassandmomentumconservationareestablishedwhiletheeffectofgas-powderflowonthemoltenpoolispresentedasaboundaryconditionequationfordevelopingthenumericalmodelofthemoltenpool.Theexperimentalresultsobtainedatvariabledefocusingamountshowthatthenegativedefocusingamountratherthanthepositiveoneissuitableforlasercladdingandthatthedefocusingamountinfluencesthemoltenheightbelowthesubstratesurface.


ExperimentalmeasuredfortheeffectsofbroadbandpulseontheB-integralofsmall-scaleself-focusingZ.Jin,X.Fu,L.Zhang,J.Deng,S.Wen,D.Fan,HunanUniv.(China)

Inhigh-powersolid-statelasers,small-scaleself-focusingisoneofthemajorfactorsfordegradationoflaserbeamandlimitingthemaximumlaserpoweravailable.Itleadstothedamageoftheelementsoflasersystemsduetoadrasticincreaseinthepeakintensityandenergydensity.Withtherapidadvancesoflaserdrivertechnology,inparticulartheemergenceofchirpedpulseamplification,thebroadbandfemtosecondlaserwasappliedinhighpowerlasersystemgradually.Itisveryimportanttorevealthecharacteristicofnonlinearsmall-scaleself-focusingofbroadbandlaserexperimentally.Inhigh-powerlasersystem,B-integralisusedtomeasuretheseverityextentofsmall-scaleself-focusingandthetypicalvalueofB-integralislessthan1.8byBeamlet,astheprototypeofNIFarchitecture,whichthenon-linearintensitygrowthisslow.

Inthispaper,weperformanexperimentalsetupfortheanalysisofmodulationgrowth,andfocusonthefeatureofmodulationgrowthofthebroadbandpulselaser.ThespatialcontrastofbroadbandpulsewithincreasingB-integralinnonlinearmediumisdiscussed.Inthecaseofthedifferentpulsewidth,comparisonofthefastestgrowingfrequencymodulationandrandomnoisemodulationcase,spatialcontrastwiththecurveofB-integralisobtainedexperimentally.ItwasfoundthatthevalueofB-integralcorrespondingtothatthespatialcontrastincreasessharplyisgreaterthanthatofnarrowbandlaserinbothcases.TherebywecanbelievethatbroadbandlasercanextendthevalueofB-integral,andthenimprovethesystemloading.


Time-resolveddigitalholographicdiagnosisoftheshockwaveinwaterinducedbyfemtosecondlaserpulsesX.Wang,P.Wang,NankaiUniv.(China)

Nowadaysthedynamicprocessesinwaterinducedbyfemtosecondlaserpulsesbecomemoreandmoreattractiveresearchtopicsduetotheirpotentialapplicationsinbiologyandmedicalfields.Itisbelievedthatthephasedistributionswillbeofmoreadvantagetopreciseandintuitivecharacterizationsoftheshockwavebehavior,comparedtoshadowgraphs.Inthispaper,time-resolveddigitalholographyisusedtorecordandinvestigatethebreakdownareainwaterinducedbya50fs,76MWlaserpulseandtwo-dimensionalphasedistributionsarereported.Experimentresultsshowthatwhentheplasmareachesacertainlength,theprofileoftheshockwaveproducedbythecentralpartoftheplasmaissimilartoacylindricalwave,whilethatproducedbythetwoendsoftheplasmawillbemorelikeasphericalwave.Furthermore,thechangesoftherefractiveindexcausedbytheformeraregreaterthanthatbythelatter,whichindicatesthattheenergyoftheshockwaveisdifferentindifferentpropagationdirections.Inaddition,theplasmaregionincreasesandtheprofileoftheoverallshockwaveapproachestoacylindricalwavewhenthelaserpowerincreases,whilethelengthoftheplasmazonedecreasesandtheprofileoftheoverallshockwaveapproachestoasphericalwavewhenthelaserpowerdecreases.Thisfurtherindicatesthattheshockwavefrontisdefinitivelydependentontheshapeoftheplasma.Theseresultsareconsistentwithoursimulationsbasedontheshockwavetransmissiontheory.Theworkprovidesanimportantexperimentalbasisforfemtosecondlaserapplicationsinbiologicalandmedicalfields.


StudyonlasercladdingofNi-basedalloyonaluminumY.Wang,N.Liu,TianjinPolytechnicUniv.(China)

InordertoimprovethesurfacePerformanceofAluminumworkpiece,ANi-CralloycoatingmetallurgicallybondedontothickAluminumplateisperformedbyYAGlaserremeltingplasmasprayingcoatingprocess.Inlasercladdingprocessing,itisdifficulttogetgoodmetallurgicalbondingbetweenthelayerandAluminum.PlasmasprayingtechnologyisusedtogetaalloylayeronthesurfaceofthickAluminumplate,andthenusingYAGlasercladdingmethodtomakeacoating.Theresultsofmicroorganizationanalysisindicatethatthecladdinglayerandsubstrateformfavorablemetallurgicalbonding,asanarrowmetallurgicalbondingzone,about3mminthickness.Thestructureofcladdinglayerismorecompactcomparedwithwitchofplasmasprayingcoating,andthecrystalgrainsarerefinedgrain.


Optimizationofreflectordesignfordiode-pumpedNd:YAGlaserwithsingle-sidepumpinggeometryK.Lee,Y.Kim,YeungnamUniv.(Korea,Republicof);H.C.Lee,J.Lee,J.Cho,HanwhaCorp.(Korea,Republicof);Y.G.Jeon,AgencyforDefenseDevelopment(Korea,Republicof);J.Yi,YeungnamUniv.(Korea,Republicof)

WetriedvariousdesignsofreflectorandreflectormaterialtogetuniformandefficientpumpingofNd:YAGrodevenwithsingle-sidepumpinggeometry.WeusedcommercialsoftwareZEMAXandLASCAD



fordesign.Thecombinedapplicationofthesoftwareenabledustoevaluatenumericallythelaserperformanceandabsorbedpumpdiodeprofile.Wetriedvariousshapeofreflectorsuchassemi-circular,square,ellipticalreflectors,andcusp-shapetogetuniformpumping.Inthecalculation,fourdiodesbarwithemissionareaof3.2mmx10mmwereconsideredtosimulatetheexperimentalresult.ForNd:YAGlasercrystal,experimentallymeasuredabsorptioncoefficient-wasusedincalculation.Inthedesign,waterflowsinsidethecoolingtubewhichsurroundstheNd:YAGrod.Forfurtherimprovementaplanar-concavewindowwasplacedinfrontofthediodetoenlargepumpbeamdivergenceangle.Thewindowimproveduniformityofpumpbeamdistributioninsidethecrystal.Inexperiment,absorbedpumpbeamdistributionwasmeasuredbyobservingflorescenceusingaCCD.Throughseveraltrialanderror,wefoundbestpumpingchamberdesignforsingle-sidepumping,whichgivesreasonablyuniformandefficientpumpingofNd:YAGrod.Q-switchedlaseroutputcharacteristicwascalculatedforvariouslasercavitydesigns.Theoutputpowerandpulsewidthwereoptimizedbyvaryingthelasercavitylengthandtheoutputcouplerreflectivity.


ResearchonlaseratmospherictransmittanceintheslantpathontheseaY.Liu,ShandongInstituteofBusinessandTechnology(China)

Inordertodeterminelasertransmitpower,laseratmospherictransmittanceintheslantpathontheseaisresearched.First,laseratmosphericattenuationontheseawasanalyzed.Then1.06mlaseratmospherictransmittanceformulaintheslantpathwasapproximativelyconcluded.1.06mlaseratmospherictransmittanceontheseawascalculated.Andthen10.6mlaseratmospherictransmittancecurvewasdescribed.Thecurveischangedbyvisibilityandpropagationdistance.Finally,somedataandconclusionsabout1.06mlaserand10.6mlaseratmosphericpropagationintheslantpathontheseawerepresented.Ithassomeextentreferencevalueforresearchonlaserweapon.


Fastaxiscouplingandphase-lockingofsemiconductorlaserbyexternal-cavityfeedbackH.Pi,ShanghaiInstituteofOpticsandFineMechanics(China)

Sincethestructurelimitation,thebeamdivergenceofsemiconductorlaserisverylarge,especiallyatthefastaxisdirection,whichresultsinasignificantrestrictiontothehighlightbeamqualityapplications.Thedivergenceangleatthefastaxisdirectioncouldbecollimatedtotensofmilliradianjustbyusingcylindricalmicro-lens.Forhigh-powerlaser-diodestacks,themethodofexternal-cavityfeedbackcouldbeappliedtorealizecross-injectionbetweenthearrays,andphase-lockingcouldbeachievedatpropercondition.Inthatcase,theoutputdivergenceanglecouldbenarrowedtoafewmilliradians.Inthispaper,weexperimentallyachievedcross-injectionbetweentwocollimatedbroad-stripediode-lasers(LDs)byemployingacommonexternalcavitymirror.Itshowedthatthefastaxisdivergenceanglesforeachlaserwerecompressedtosomeextent,andthecenterwavelengthstendedtounanimity.Thetheoreticaldiscussionwasalsogiven,showinggoodagreementwiththeexperimentalresults.Ourresearchwouldbenefittoenhancethebeamqualityofthehigh-powerlaserdiodebarstacks.


LaserdopingofphosphorousingroovedsiliconesurfaceK.Lee,S.Bae,Y.Kim,Y.Joh,J.Yi,YeungnamUniv.(Korea,Republicof);M.Jeon,J.Lee,J.Hong,MillinetSolar(Korea,Republicof)

Amongvarioustrialsonimprovingenergyconversionefficiencyofsiliconebasedphoto-voltaiccell,laserdopingcastspromisingfuture.Severalresearchgroupsaresuggestingtheirownmethodsforlaserdoping.Usually,dopinglaserisinjectedinsideofnarrowphosphoricacidjet.Theinjectedbeampropagatesthroughthejetanditgroovessurfaceofsiliconecell.Thelaserenergyalsoheatsthesiliconesurfaceandphosphorousispenetratedthroughthesurface.Inthiswork,weseparatethegroovinglaserandheatinglaser.Thesiliconesurfacewasgroovedbyapulsedfiberlaser.Thespotsizeofthelaserwas50m.Forsurfacemeasurement,groovedwithof200mwasneeded.Tohavethegroovewidth,wescannedthelaserseveraltimes.SEMimageofthegroovedsurfaceshowedrippleofthesurface.Thephosphoricacidwassprayedonthegroovedsurface.AfibercoupledcwdiodelaserheatedthesprayedSisurface.Afterheating,theSiwaswashedthoroughlybydeionizedwater.ThedepthprofileofpenetratedphosphorouswasexaminedbyusingSIMS.Theprofileindicatedthatphosphorouswaspenetratedabout50nm.Fourpointmeasurementofsurfaceresistancealsoindicatedsuccessfullaserdoping.


AnalysisandsimulationofstimulatedBrillouinscatteringinall-fibersingle-frequencyfiberamplifierswithdeliveryfibersJ.Leng,NationalUniv.ofDefenseTechnology(China)

Thepumpcombinerisoneofthekeycomponentsintheall-fibersingle-frequencyfiberamplifiers,whichcouplesthepumppowerintotheinnercladofthedoublecladfiber.Atthesametime,deliveryfibersaredrawninbythepumpcombiner.Inthispaper,theinfluenceofthedeliveryfibersonstimulatedBrillouinscattering(SBS),whichmitigatesthesignalpowerintoreversedirectionandlimitsthemaximaloutputpowerandevencausespotentialdamagetoopticalcomponents,isdiscussed,basedontherate-equationscombiningwithSBS.Theimpactsofpumpschemesaresimulated,togetherwithlengthsandgeometricalstructuresofdeliveryfiber.Theresultsindicatethattheamplifierperformanceisconsiderableunderminebythedeliveryfiberinabackwardpumpedamplifier,inwhichthelengthsandcorediameterofthedeliveryfibermakegreatimpactsontheperformance.Ontheotherhand,theperformanceisalmostnotconfinedaforwardpumpedamplifier.Theimpactsofthetemperatureandstraingradientsalongthefiber,whichcanbroadentheSBSgainprofileandtherebysuppressSBS,ontheamplifierperformancesarediscussed.Suitablesuppressionschemeisproposedtoovercometheinfluencesofdeliveryfiberontheamplifierperformance.


Microstructureandhigh-temperatureoxidationresistanceofTiN/Ti3AlintermetallicmatrixcompositecoatingsonTi6Al4ValloysurfacebylasercladdingH.Liu,KunmingUniv.ofScienceandTechnology(China)

Ahigh-temperatureoxidationresistantTiNembeddedinTi3Alintermetallicmatrixcompositecoatingwasfabricatedontitaniumalloy



Ti6Al4Vsurfaceby6kWtransverse-flowCO2laserapparatus.Thecomposition,morphologyandmicrostructureofthelasercladTiN/Ti3Alintermetallicmatrixcompositecoatingwerecharacterizedbyopticalmicroscopy(OM),scanningelectronmicroscopy(SEM),X-raydiffraction(XRD)andenergy-dispersivespectrometer(EDS).Inordertoevaluatethehigh-temperatureoxidationresistanceofthecompositecoatingsandthetitaniumalloysubstrate,isothermaloxidationtestwasperformedinaconventionalhigh-temperatureresistancefurnaceat600and800,respectively.Theweightgainsweremeasuredusingahighaccuracyphotoelectricbalanceandtherelativehigh-temperatureoxidationresistancewasalsousedtocharacterizetheoxidationresistanceofthelasercladTiN/Ti3Alintermetallicmatrixcompositecoating.

TheresultshowthatthelasercladintermetalliccompositecoatinghasarapidlysolidifiedfinemicrostructureconsistingofTiNprimaryphase(granular-like,flake-like,anddendrites),anduniformlydistributedintheTi3Almatrix.ItindicatesthataphysicalandchemicalreactionbetweentheTipowderandAlNpowderoccurredcompletelyunderthelaserirradiation.Inaddition,themicrohardnessoftheTiN/Ti3Alintermetallicmatrixcompositecoatingisabout900HV,4timeshigherthanthatofthetitaniumalloysubstrate.Thehigh-temperatureoxidationresistancetestrevealsthatTiN/Ti3Alintermetallicmatrixcompositecoatingresultsinthebettermodificationofhigh-temperatureoxidationbehaviorthanthetitaniumsubstrate.Theexcellenthigh-temperatureoxidationresistanceofthelasercladisattributedtotheformationofthereinforcedphaseTiNandAl2O3,TiO2hybridoxide.Therefore,thelasercladTiN/Ti3Alintermetallicmatrixcompositecoatingisanticipatedtobeapromisingoxidation-resistingsurfacemodificationtechniqueforTi6Al4Valloy.


StudyontemperaturefiledofnodularcastironinlasertransformationhardeningS.Hu,HunanUniv.(China)

Inthispaper,thetemperaturefieldofnodularcastironinlasertransformationhardeningwasinvestigated.ThetemperaturefieldwasmodelledandcalculatedwithanANSYSsoftware.Inthepresentedexperiments,colorimetrictemperaturemeasurementmethodwithCCDwasappliedtoobtainthetemperaturefield.Thecalculatedresultsagreedwelltotheexperimentalones.Themodelwouldhelppredictthewidthanddepthofthehardenedtrackanditsmicostructureandproperties.


ApproximatecalculationofpulselaserheattreatmentY.Wu,TheAcademyofEquipmentCommand&Technology(China);J.Li,Y.Fu,KunmingUniv.ofScienceandTechnology(China)

Duringtheresearchofthelasersurfaceheattreatmentofamaterial,thetemperaturefieldisanimportantparametertodeterminethethermaleffect.Duetothecomplexityofheatinteractionbetweenthelaserbeamandthematerial,theirradiatedworkpieceisregardedasthehomogeneousmediumwithconstantthermophysicalpropertiesandtheintensitydistributionoflaserbeamisconsideredasanidealdistributionsoastosimplifythecalculation.Butlaserbeamintensityis,infact,notalwaysidealdistribution.Therefore,itisacrucialtasktostudythecalculationmethodoftime-dependenttemperaturefieldsbyusingrealbeamintensitydistribution.Inourstudy,thelaserbeamintensityisregardedassuperimpositionofTEM00andTEM01intermofthecertainproportion.Throughthesuperimpositionfactorsadjustment,wecanwellexpressthelaserbeamintensitydistributionwiththelow-ordermodeoutput.Thesemi-analyticalcalculationformula

ofpulselaserheatingisalsore-deduced,whichissuitableforthiskindoflaserdevice.Andtheheattreatmentexperimentsofsteelweredonesoastoprovethefeasibilityofthetheoreticalstudy.Inordertoletourinvestigationresultsbeadaptedforlaserbeamwitharbitraryintensitydistribution,theapproximateexpressionsofarbitrarydistributionoflaserbeamandthemethodofdeterminingthethermophysicalparametersofthematerialthroughtheexperimentsarediscussed.

Thepaperisorganizedasfollows:Sectiondescribesthepresentresearchesaboutthecalculationoflaserheattreatment,andprovidesourmethod.Sectionproposesthecalculationmodelofpulselaserheattreatment.TheexperimentalverificationbasedonthephasetransformationmodelAC1isgiveninsection.TheapproximateexpressionsofarbitrarydistributionoflaserbeamandthemethodofdeterminingthethermophysicalparametersofthematerialthroughtheexperimentsarediscussedinSection.Sectionisourconclusion.


SimulationandmeasurementoftemperaturefieldofnodularcastironinlasertransformationhardeningS.Hu,HunanUniv.(China)

Onthebasisofconsideringthethermalphysicalparametersofmaterial,thelatentheatandtheeffectofconvectionradiation,ANSYSparametricdesignlanguageisusedtoestabishathree-dimensioncomputingmodeloftransientmovingtemperaturefieldofnodularcastironinlasertransformationhardening.Thetemperaturefieldchangeinthelasertransformationhardeningprocesswasanalyzed.Thenthetrichromatric(RGB)imageintheprocesswasacquiredbycolor-CCDandthestrengthvalueofmonochromatricradiationwascalculated.Thetestspecimenofnodularcastironwasassumedtobethegreybody.Accordingtotheprincipleofcolorimetrictemperaturemeasurement,thetemperaturewasobtainedandshown.Therelationofsimulatedresultsandtheexperimentalresultswasfoundbycompareingwiththem.Thenthewidthofthehardenedtrackcanbepredictedbytheexperimentalresults.Thiswouldhelpanalysetheeffectofprocessparametersandcarryoutreal-timemeasureandcontrolinlasertransformationhardeningprocess.


ExperimentalInvestigationonmultiwavelengthRamanfiberlaserbasedonchirpedFBGandsagnacfilterZ.Qin,GuilinUniv.ofElectronicTechnology(China);X.Zhou,Univ.ofElectronicScienceandTechnologyofChina(China)

ItisextremelyusefultofabricatemultiwavelengthlasersbasedonstimulatedRamanscatteringinopticalfiberssincetheRamanfibershaveseveraladvantagessuchasstableoperationatroomtemperatureandlargegainbandwidth.AbroadbandchirpedfiberBragggratingandasagnacloophavebeenutilizedtoformalinearRamancavitytogenerateamultiwavelengthfiberlaser.Toexploretheimpactsoffour-wavemixingprocessesontheRamanfiberlaser,alengthofdispersion-shiftedfiber(DSF)isincorporatedintothelaseroscillator.TheintegratingRamangainofDSFissmallincomparisonwiththeRamangainmediaforthepurposeoflimitingitsRamancontributiononStokeswaves.Experimentalresultsshowthatforagivenpumplevelfour-wavemixinginteractionsinducedbyDSFplayaroleofbroadeningtheStokesspectrumandoutputingmorewavelengthsthanthecasewithoutDSF.




PMMAtransmissionweldingwithfiberlasersJ.Jiao,InstituteofIndustryTechnology(China);X.Wang,HuazhongUniv.ofScienceandTechnology(China);X.Bai,C.Peng,InstituteofIndustryTechnology(China)

Nowadays,plasticiswidelyusedinareasofautos,medicaldevices,electronicdevices,etal.Weldingplasticwithlasersbecomemoreandmorepopular,especiallytheplastictransmissionweldingwithnear-infraredlasers.Inpreviousstudies,thelaserbeamwasalwaystreatedasasurfacesource,whichnotagreeswellwiththepracticalexactly.Inthispaper,thelasersourcewastreatedasavoluminalsourceinthetransmissionpartandasurfacesourceintheabsorptionpart.Themathematicalmodelofplasticlasertransmissionwelding(LTW)wasproposed,andthethermalbehavioroftheweldingprocesswassimulatedbyusingfiniteelementmethod(FEM)softwareANSYS.Thewideoftheweldingpathandthetemperatureoftheheatedzonefordifferentparameterswerepredictedbynumericalmethod.Underthedirectionofthenumericalresults,PMMAmaterialwasweldedwithfiberlasers.Theweldingqualitywastestedbymicroscope,whichagreeswellwiththenumericalpredicting.


AberrationscorrectionofaNd:YAGslabamplifierusingacompactadaptiveopticssystemP.Yang,L.Dong,X.Lei,N.Yu,W.Liu,B.Xu,InstituteofOpticsandElectronics(China)

Zigzagslablaseramplifierispromisinglaserarchitectureforachievinghighpowerandhighqualitybeamoutput.Comparedwithitscounterpartssuchasrodlasers,disclasers,thedistortionsgeneratedinthezigzagslabaremuchsmalleratthesamepowerlevelduetoitsbettercoolingmeansandconvenientthermalmanagement.However,itisshouldalsobenotedthatmanydetrimentalfactorssuchasthermallyinducedstrainanddistortions,staticaberrationsfromtheopticalcomponentsandsoonwouldinducewave-frontdistortionsinthelaserfieldandreducetheoutputbeamquality.Therefore,manyresearchershavebeenengagingindevelopingtechniquestoimprovetheperformanceofzigzagslabamplifierstothebestoftheirability.Generally,itisdifficulttocompensateforallthewave-frontdistortionsthatgeneratedintheslablaserjustthroughpassivemethods,especiallyforthosedynamicthermaldistortions.Toofferapromisingalternative,weemploytheactivemethodbasedonadaptiveoptics(AO)tocorrectthedistortionsinazigzagslabamplifier.ThisAOsystemmainlyincludesa39-elementrectangulardeformablemirror(DM),afar-fielddetector,andastochasticparallelgradientdescent(SPGD)optimizationalgorithm.WhatisdifferentfromthoseconventionalAOsystemsusedinmanyfieldsisthatthiswave-frontsensor-lessSPGDAOsystemdoesnotneedanywave-frontsensorstomeasurewave-frontinformation,butusethefar-fieldmetricwhichismainlydeterminedbythebeamqualitytocontroltheDMandachievedistortionscorrection.Thisstrategyislowcostandcompacttoimplementinthezigzagslabamplifiersystem.


Differenttypesofsidebandgenerationinapassivelymode-lockedsolitonfiberlaserH.Li,Z.Jing,J.Liao,X.Tang,R.Lu,Y.Liu,Univ.ofElectronicScienceandTechnologyofChina(China)

Femtosecondmode-lockedfiberlasershaveattractedagreatdealofinterestbothasadvancedphotonicdeviceswitharangeofresearch

andindustrialapplicationsandalsoasaninterestingnonlinearphysicalsystemtostudy.Herewereportontheexperimentalobservationofsidebandgenerationinapassivelymode-lockedsolitonfiberlaser.ThelaserusedinthisstudyhasacavityconfigurationtypicalforEr-dopedfiberringlasersusingthenonlinearpolarizationrotationtechniqueformodelocking.Self-startingandstablemode-lockingoperationiseasilyachievedinthelaser.Theoutputsolitonpulseshaveadurationofabout300fsandarepetitionrateof13.7MHzat1560-nmwavelength.Detailedspectralandtransientdynamicsofthelaseraremeasuredatdifferentpumpinglevels.Asthepumppowerisincreasedandthepolarizationcontrollerisadjusted,thesolitonpeakpowerincreases,andthesidebandsofthesolitonspectrumchangefromtheKellysidebandswithspectralpeakstotheparametricsidebandswithspectraldips.Thedip-typesidebandshaveclearlydifferentcharacteristicstothoseoftheKellysidebands.WenumericallysimulatedthesolitonoperationofthefiberlaserbasedonthecoupledGinzburg-Landauequations.Thesimulationresultsareconsistentwiththeexperimentalobservations,whichconfirmthatdip-typespectralsidebandscanappearonthesolitonspectrumofauniformsoliton-emissionfiberlaser.


FarfieldirradianceprofilecontrolwithhighspatialfrequencydeformablemirrorD.E.Wang,D.Hu,W.Dai,P.Li,J.Zhao,Q.Yuan,F.Jing,X.Li,ChineseAcademyofEngineeringPhysics(China)

Anovelmethodbasedondiffractiontheorytocontrolthefar-fieldirradianceprofilebydeformablemirrorispresented.Specialnear-fieldphasewhichdeterminesthecontourofthefocalspotisobtainedbyahighspatialfrequencydeformablemirror.Numericalsimulationsshowthat,wecancontrolthefar-fieldintensityenvelopeasCPPbyadoptingadaptiveopticstechniquewhenthespatialresolutionofdeformablemirrorishighenough,here1616actuatorsin320mm320mmaperture.Thecouplingcoefficientisanimportantfactorinfluencingcontroleffect,anditsbestvaluerangeisround0.6.


SuppressionoftransversestimulatedRamanscatteringortransversestimulatedBrillouinscatteringY.Zhang,H.Ye,X.Yan,M.Wang,J.Zheng,M.Li,F.Jing,X.Wei,ChineseAcademyofEngineeringPhysics(China)

Anovelmethod,bywhichtheedgeofthefrequencyconvectorisprocessedintoarris,hasbeenproposedtosuppressthereflectionoftransversestimulatedRamanscatteringortransversestimulatedBrillouinscatteringattheedge.Themodeanalysisindicatesthattheresidualreflectiondecreasesexponentiallywiththeangleofthearrisbythismethodandthedirectionofthelightfinallyreflectedbackhasananglewiththesurfaceofconvector.

7843-28, Session 5

ExperimentalstudyofmonitoringplasmalightinlasercladdingL.Hong,Z.Hu,B.Ma,G.Song,ShanghaiMaritimeUniv.(China)

Lasercladdingmonitoringisoneofthecladdinglayerqualitycontrollingmethods.Atpresent,claddingmonitoringusuallymonitorthetemperatureortheshapeofmeltingpool.Theheightdeviationbetweenmeltedandunmeltedpointisalsoconsidered.Inthispaper,optical



signalofplasmawhichisoneofthecharacteristicsignalofplasmahasbeendetectedbyphototubeincladding.Therelationshipbetweenblue-violetlightintensityandlaserpowerscanvelocityhasbeendiscussed,andtherelevancebetweenqualityoflayerandintensityhasbeenanalysedaswell.Theresultsindicatethatwhilelaserpowergrowedtheintensityincreasedjustatalowrate,andtheintensitydecreasedasscanvelocityincreasedwhenthepowerislowerthanadefinitevalue.Butwhenthepowerisgreaterthanthisvaluetheintensitywillriseasvelocityincrease.Thequalityoflayerisimprovedgreatlywhentheintensityvaluerangfrom1.7to2.5withaslightfluctuation.

7843-30, Session 5

NumericalsimulationofcurvedsurfaceofgearinlasercladdingZ.Hu,L.Hong,G.Wu,ShanghaiMaritimeUniv.(China)

Mostofthetemperatureandstressfieldssimulationsinlasercladdingwerebasedonflatsurface,whileactuallycladdingmayoccuronanycurvedsurface.Thedifferencebetweencladdingonflatsurfaceandcurvedsurfaceisthatthelatterwillresultinunevendistributionoflaserpower.Experimentsoflasercladdinghavebeendoneondifferentmaterialgearsundervarioustechnicalconditions,andcrackleshavebeenobservedbySEM.Somefactorsthataffectlaserpoweractually,suchaslasershielding,theincidentangleoflaserandcurvedsurfaceofgearareallconsidered.Basedtheanalysisoftheshapeoflayeraftercladdingandthephasetransformaionduringcladding,temperatureandstressfieldsofgearsurfacelasercladdinghavebeensimulatedbyANSYSinthisarticle.Theresultsindicatethatappropriatematerialmatchingandbasepreheatingcandecreasethelikelihoodofcrackles,eveneliminateit.

7843-31, Session 5

ShockinducedphenomenainhighfluencefemtosecondlaserablationofsilicaglassX.Wang,NankaiUniv.(China)

Shadowgraphsofdynamicprocessesoutsideandinsidethetargetduringtheintensefemtosecondlaserablationofsilicaglassatdifferentenergyfluencesarerecorded.Twomaterialejectionsoutsidethetargetandtwocorrespondingstresswavesinsidethetargetareobserved.Inparticular,athirdstresswavecanbeobservedatenergyfluenceashighas40J/cm2.Thepressure,thetemperature,thefreeelectrondensity,andtheioniccomponentsatthelaserpulseendareestimated,basedonwhichthemechanicalreactionofthelaserheatedmaterialisinvestigated.Accordingtoouranalysis,thefirstwaveisathermoelasticwave,whilethesecon

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