简介：Thebehaviorofthestressintensityfactoratthetipsofcrackssubjectedtouniaxialtensionσχ^∞=pwithtraction-freeboundaryconditioninhalf-planeelasticityisinvestigated.Theproblemisformulatedintosingularintegralequationswiththedistributiondislocationfunctionasunknown.Intheformulation,wemakeusedofamodifiedcomplexpotential.Basedontheappropriatequadratureformulastogetherwithasuitablechoiceofcollocationpoints,thesingularintegralequationsarereducedtoasystemoflinearequationsfortheunknowncoefficients.Numericalexamplesshowthatthevaluesofthestressintensityfactorareinfluencedbythedistancefromthecrackstotheboundaryofthehalf-planeandtheconfigurationofthecracks.

简介：TheaveragepoweroffiberlasershasbeenscaleddeeplyintothekWregimeinthepastyears.However,stimulatedRamanscattering(SRS)isstillamajorfactorlimitingfurtherpowerscaling.Here,wehavedemonstratedforthefirsttime,tothebestofourknowledge,thesuppressionofSRSinahalf10kWtandempumpingfiberamplifierusingchirpedandtiltedfiberBragggratings(CTFBGs).Withspeciallyself-designedandmanufacturedCTFBGsinsertedbetweentheseedlaserandtheamplifierstage,amaximumSRSsuppressionratioof>15dBinspectrumisobservedwithnoreductioninlaserefficiency.WithoneCTFBG,theeffectiveoutputpowerisimprovedto3.9kWwithabeamqualityM2factorof~1.7from<3.5kWwithanM2factorof>2;withtwoCTFBGs,theeffectivelaserpowerreaches4.2kWwithanincreasingratioof20%andanM2factorof~1.8,andfurtherpowerimprovementislimitedbythepowerandperformanceofthe1018nmpumpsources.ThisworkprovidesaneffectiveSRSsuppressionmethodforhigh-powerall-fiberlasers,whichisusefulforfurtherpowerscalingofthesesystems.