简介:Oxygen-containingdefectsareveryimportantforalteringthenonlinearoptical(NLO)propertiesofgraphene.Toinvestigatethecorrelationbetweenoxygen-containingdefectsandthesynergisticNLOresponseingraphenebasednanocomposites,weattachedCdSnanocrystalsonthesurfaceofgraphene(G)andpreparedG/CdSnanohybrids(NHs)consistingofvariousoxygen-containingfunctionalgroupsviaachemicalmethod.TheNLOabsorptionandrefractionofG/CdSNHsundersinglepulselaserirradiationareenhancedby10.8timeswiththeconcentrationdecreaseofsurfaceoxygen-containinggroups,whichmightbeattributedtothelocalfieldeffectsandsynergeticeffectsstemmingfromchargetransferbetweenthetwocomponents.However,theopticalnonlinearityisdecreasedwithfurtherconcentrationdecrease,whichmightarisefromsp~2fragmentinterconnectionandsurfacedefectsintheNHs.TheNLOabsorptiontransformationfromtwo-photonabsorptiontosaturableabsorptionwithoxygendecreaseisobserved,andintensity-relatedNLOabsorptionandrefractioninNHsarealsodiscussed.Meanwhile,theG/CdSNHsexhibitsuperiorNLOproperties,implyingpotentialapplicationsofNHmaterialinNLOdevices.
简介:Weexperimentallydemonstrateforthefirsttime,tothebestofourknowledge,anall-fiberpassivelymode-lockedlaseroperationbasedonthenonlinearmultimodeinterferenceofstep-indexmultimodefiber.Suchastructurecouplesthelightinandoutofthemultimodefiberviasingle-modefibers,anditsphysicalmechanismsforsaturableabsorptionhavebeenanalyzedtheoreticallybasedonthethird-ordernonlinearKerreffectofmultimodefiber.Usingthenonlinearmultimodeinterferencestructurewith48.8mmlengthstep-indexmultimodefiber,themodulationdepthhasbeenmeasuredtobe~5%.Thepassivelymode-lockedlaseroutputpulseshaveacentralwavelengthof1596.66nm,bandwidthof2.18nm,pulsewidthof~625fs,andfundamentalrepetitionrateof8.726MHz.Furthermore,theinfluenceoftotalcavitydispersionontheopticalspectrum,pulsewidth,andoutputpowerisinvestigatedsystematicallybyaddingdifferentlengthsofsingle-modefiberanddispersioncompensationfiberinthelasercavity.
简介:Two-dimensional(2D)materialshaveemergedasattractivemediumsforfabricatingversatileoptoelectronicdevices.Recently,few-layermolybdenumdisulfide(MoS2),asashining2Dmaterial,hasbeendiscoveredtopossessboththesaturableabsorptioneffectandlargenonlinearrefractiveindex.Herein,takingadvantageoftheuniquenonlinearopticalpropertiesofMoS2,wefabricatedahighlynonlinearsaturableabsorptionphotonicdevicebydepositingthefew-layerMoS2ontothemicrofiber.WiththeproposedMoS2photonicdevice,apartfromtheconventionalsolitonpatterns,themode-lockedpulsescouldbeshapedintosomenewsolitonpatterns,namely,multiplesolitonmolecules,localizedchaoticmultipulses,anddouble-scalesolitonclusters.Ourfindingsindicatethatthefew-layerMoS2-depositedmicrofibercouldoperateasapromisinghighlynonlinearphotonicdevicefortherelatednonlinearopticsapplications.
简介:Wedemonstrateapassivelymode-lockedall-fiberlaserincorporatingapieceofgraded-indexmultimodefiberasamode-lockingmodulatorbasedonanonlinearmultimodalinterferencetechnique,whichgeneratestwotypesofcoexistinghigh-energyultrashortpulses(i.e.,theconventionalsoliton(CS)andthestretchedpulse(SP))TheCSwithpulseenergyashighas0.38nJisobtainedatthepumplevelof130mW.Whenthepumpincreasesto175mW,thehigh-energySPoccursatasuitablenonlinearphasebiasanditspulseenergycanreach4nJata610mWpump.ThepulsedurationsofthegeneratedCSandSPare2.3psand387fs,respectively.Thetheoryofnonlinearfiberoptics,single-shotspectralmeasurementbythedispersiveFourier-transformtechnique,andsimulationmethodsbasedontheGinzburg–LandauequationareprovidedtocharacterizethelaserphysicsandrevealtheunderlyingprinciplesofthegeneratedCSandSP.Aroguewave,observedbetweentheCSandSPregions,mirrorsthelaserphysicsbehindthedynamicsofgeneratingahigh-energySPfromaCS.Theproposedall-fiberlaserisversatile,cost-effectiveandeasytointegrate,whichprovidesapromisingsolutionforhigh-energypulsegeneration.
简介:MakinguseoftheZ2×Z2symmetry,wecouldstudythestructurenearmultipleS-treakingturningpoints.Inparticular,weshowthatthereexisttwokindsofsingularpointpaththroughdoubleSbreakingturningpointsandtripleSbieakingturningpoints,onetsquadraticturningporntpathandoneisquadraticpitchforkbifurcationpointpath.SomesimpleregularextendedsystemstocornputedoubleandtripleS-breakingturningpointsareproposed.Numericalexamplesarealsogreen
简介:Fortwo-dimensionnonlinearconvectiondiffusionequation,atwo-gridmethodofcharacteristicsfinite-elementsolutionwasconstructed.Inthismethodthenonlineariterationsisonlytoexecuteonthecoarsegridandthefine-gridsolutioncanbeobtainedinasinglelinearstep.Forthenonlinearconvection-dominateddiffusionequation,thismethodcannotonlystabilizethenumericaloscillationbutalsoacceleratetheconvergenceandimprovethecomputationalefficiency.Theerroranalysisdemonstratesifthemeshsizesbetweencoarse-gridandfine-gridsatisfythecertainrelationship,thetwo-gridsolutionandthecharacteristicsfinite-elementsolutionhavethesameorderofaccuracy.Thenumericalexampleconfirmsthatthetwo-gridmethodismoreefficientthanthatofcharacteristicsfinite-elementmethod.
简介:Aself-adaptiveprecisealgorithminthetimedomainwasemployedtosolve2-Dnonlinearcoupledheatandmoisturetransferproblems.Byexpandingvariablesatadiscretizedtimeinterval,thevariationsofvariablescanbedescribedmoreprecisely,andanonlinearcoupledinitialandboundaryvalueproblemwasconvertedintoaseriesofrecurrentlinearboundaryvalueproblemswhicharesolvedbyFEtechnique.Inthecomputation,noadditionalassumptionandthenonlineariterationarerequired,andacriterionforself-adaptivecomputationisproposedtomaintainsufficientcomputingaccuracyforthechangesizesoftimesteps.Inthenumericalcomparison,thevariationsofmaterialpropertieswithtemperature,moisturecontent,andbothtemperatureandmoisturecontentaretakenintoaccount,respectively.Satisfactoryresultshavebeenobtained,indicatingthattheproposedapproachiscapableofdealingwithcomplexnonlinearproblems.
简介:Inthepaper,thenonlinearmagnetoelasticpropertiesofcompositionTb0.27Dy0.73Fe1.95<110>orientedpolycrystallinealloysareinvestigatedundercoupledloadsofhighmagneticfieldandcompressivestress.Themagnetizationandmagnetostrictionaremeasuredsimultaneouslyunderappliedmagneticfieldfrom800to800kA/mandcompressivestressfrom0to25MPaatroomtemperature.Thestraincoefcientandrelativepermeabilityareobtainedbydiferentialcalculationfromtheexperimentalcurves.Theresultsshowthatthevaluesofsaturationmagnetization(Ms)underdiferentcompressivestressesremaininvariablyconstantintheregionofthehighmagneticfield.Thesaturationmagnetostriction(λs)increaseswithincreasingcompressivestressandreaches1680×106under25MPa.Accordingtotheincreaseofthecompressivestress,thehystereticloopareaofmagnetizationandmagnetostrictionincreases,whilethemaximumrelativepermeabilityandstraincoefcientdecrease.Additionally,theinfluenceofthebiasmagneticfieldonthemechanicalpropertyistakenintoaccount.Thestress-strainrelationshipisnonlinearandsensitivetotheappliedexternalmagneticfieldsalongtheaxisofrod.Theresultsobtainedareausefulcomplementtotheexistingexperimentsfortheoreticalapproachesandengineeringapplications.
简介:Inthispaper,bothnonlinearsaturableabsorptionandtwo-photonabsorption(TPA)offew-layermolybdenumdiselenide(MoSe2)wereobservedat1.56μmwavelengthandfurtherappliedtomode-lockedultrafastfiberlaserforthefirsttimetoourknowledge.Few-layerMoSe2nanosheetswerepreparedbyliquid-phaseexfoliationmethodandcharacterizedbyxraydiffractometer,Ramanspectroscopy,andatomicforcemicroscopy.TheobtainedfewlayerMoSe2dispersionisfurthercompositedwithapolymermaterialforconvenientfabricationofMoSe2thinfilms.Then,weinvestigatedthenonlinearoptical(NLO)absorptionpropertyofthefew-layerMoSe2filmusingabalancedtwin-detectormeasurementtechnique.BoththesaturableabsorptionandTPAeffectsofthefew-layerMoSe2filmwerefoundbyincreasingtheinputopticalintensity.Thesaturableabsorptionshowsamodulationdepthof0.63%andalownonsaturablelossof3.5%,correspondingtotherelativemodulationdepthof18%.TheTPAeffectoccurredwhentheinputopticalintensityexceeds260MW∕cm2.Furthermore,weexperimentallyexploitthesaturableabsorptionoffew-layerMoSe2filmtomodelockanall-fibererbium-dopedfiberlaser.Stablesolitonmodelockingat1558nmcenterwavelengthisachievedwithpulsedurationof1.45ps.ItwasalsoobservedthattheTPAprocesssuppressesthemode-lockingoperationinthecaseofhigheropticalintensity.OurresultsindicatethatlayeredMoSe2,asanothertwo-dimensionalnanomaterial,canprovideexcellentNLOproperties(e.g.,saturableabsorptionandTPA)forpotentialapplicationsinultrashortpulsegenerationandopticallimiting.
简介:Amode-lockedthulium-dopedfiberlaser(TDFL)basedonnonlinearpolarizationrotation(NPR)withdifferentnetanomalousdispersionisdemonstrated.Whenthecavitydispersionis-1.425ps~2,thenoise-like(NL)pulsewithcoherencespikewidthof406fsandpulseenergyof12.342nJisgeneratedatacenterwavelengthof2003.2nmwith3dBspectralbandwidthof23.20nm.Intheexperimentalperiodof400min,the3dBspectralbandwidthvariation,theoutputpowerfluctuation,andthecentralwavelengthshiftarelessthan0.06nm,0.04dB,and0.4nm,respectively,indicatingthattheNPR-basedTDFLoperatingintheNLregimeholdsgoodlong-termstability.
简介:Liquid-phase-exfoliationtechnologywasutilizedtopreparelayeredMoS2,WS2,andMoSe2nanosheetsincyclohexylpyrrolidone.Thenonlinearopticalresponseofthesenanosheetsindispersionswasinvestigatedbyobservingspatialself-phasemodulation(SSPM)usinga488nmcontinuouswavelaserbeam.ThediffractionringpatternsofSSPMwerefoundtobedistortedalongtheverticaldirectionrightafterthelasertraversingthenanosheetdispersions.Thenonlinearrefractiveindexofthethreetransitionmetaldichalcogenidesdispersionsn2wasmeasuredtobe10-7cm2W-1,andthethird-ordernonlinearsusceptibilityχ(3)10-9esu.TherelativechangeofeffectivenonlinearrefractiveindexΔn2e∕n(2e)oftheMoS2,WS2,andMoSe2dispersionscanbemodulated0.012–0.240,0.029–0.154,and0.091–0.304,respectively,bychangingtheincidentintensities.Ourexperimentalresultsimplynovelpotentialapplicationoftwo-dimensionaltransitionmetaldichalcogenidesinnonlinearphasemodulationdevices.
简介:Bytheadditionalreactionofbinuclearcompounds(Me4N)2M2S4(TDT)2(M=Mo,W;H2TDT=H2CH3C6H3S2)withmononuclearcuprouscomplex,twonewM-Cu-SclustersMo2Cu2S4(TDT)2-(PPh3)2·CH3CH2OH(1)andW2Cu2S4(TDT)2(PPh3)2·0.5CH3CH2OH-0.5H2O(2)havebeenpreparedandcharacterizedbyIR,UV-Vis,31PNMRspectroscopy,cyclicvoltammetryandsinglecrystalX-raystructureanalysis.BothcompoundscrystallizeinspacegroupP21/nwithlatticeparametersa=1.0956(3),b=2.2072(3),c=2.4340(3)nm,β=100.36(2)°,V=5.790(3)nm3andZ=4for1anda=1.0965(9),b=2.2135(3),c=2.4317(4)nm,β=99.63(8)°,V=5.819(8)nm3andZ=4for2.Bothmolecularstructurescontainacubane-likeclustercore[M2Cu2S4](M=Mo,W)andtheirskeletonsarealmostthesameexceptforMatoms.Thesyntheses,structuresandspectrumcharacterizationsofthesetwoclustersarediscussed.Thethird-ordernonlinearoptical(NLO)propertyofthetwoclusterswasstudiedbythetechniqueofforwarddegeneratefour
简介:Inthispaper,weinvestigatethetravelingwavesolutionsforthenonlineardispersiveequation,Korteweg-deVriesZakharov–Kuznetsov(KdV-ZK)equationandcomplexcoupledKdVsystembyusingextendedsimplestequationmethod,andthenderivethehyperbolicfunctionsolutionsincludesolitonsolutions,trigonometricfunctionsolutionsincludeperiodicsolutionswithspecialvaluesfordoubleparametersandrationalsolutions.Thepropertiesofsuchsolutionsareshownbyfigures.Theresultsshowthatthismethodisaneffectiveandapowerfultoolforhandlingthesolutionsofnonlinearpartialdifferentialequations(NLEEs)inmathematicalphysics.