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1、August15,1998/Vol.23,No.16/OPTICSLETTERS1307High-efficiencyvolumehologramrecordingwithapulsedsignalbeamGuoqiangLi,LirenLiu,BoLiu,andZhizhanXuShanghaiInstituteofOpticsandFineMechanics,AcademiaSinica,P.O.Box800-211,Shanghai201800,ChinaReceivedMarch31,1998Wepres
2、entanefficientphotorefractivevolumehologramrecordingtechniquewithapulsedsignalbeamandcontinuousreference-beamillumination.Thegratingenvelopecanbesimplycontrolledbymanipulationofthedutycycleofthesignalbeam.Thus,foranygratingcouplingstrengthanddifferentinitialr
3、eference-signalintensityratios,thediffractionefficiencycanbemaximizedwiththistechniqueandcanbegreatlyincreasedincomparisonwiththatoftheconventionalrecordingtechnique.ã1998OpticalSocietyofAmericaOCIScodes:200.4740,190.5330.Recentlythestudyofphotorefractivevolu
4、meholo-Intheproposedpulsedrecordingschemetherefer-gramshasspurredagreatdealofinterestbecauseofencebeamilluminatesthephotorefractivecrystalcon-theirlargecapacityforparallelopticalinterconnectiontinuouslywhilethesignalbeamperiodicallyinteracts1±5anddatastorage.
5、Itiswellknownthatavolumewiththemedium,asshowninFig.1.Ineachperiodhologramcanbeformedbyinterferenceoftwobeams.thesignalbeamisincidentuponthecrystalforadu-Higherdiffractionefficiency(DE)isdesiredforapplica-rationP1DtandisblockedforadurationP2Dt,where6±11tions.H
6、owever,inpractice,inmanycasestheDEDtisatimeintervalthatisshortcomparedwiththeisnothighwhentheconventionalcontinuousrecord-response-timeconstanttofthecrystalandP1andingmethodisused.ThegratingenvelopeisstronglyP2areintegers.Theexposuresequencecanberep-dependent
7、onthecouplingstrengthandtheinitialresentedas12reference-signalbeam-intensityratior0.Especially"#X1`t2PDty22ksP1PdDtwhenr0#1,thegratingamplitudeisconcentratedAstd•rect112.(2)onlynearthefrontsurfaceofthecrystal,andthesPDtk•01DEcanberatherlow.Forthisreasonadoubl
8、e-sided7±10alternatereadingschemewassuggestedforen-Duringtherecording,transientsArsz,tdandAssz,tdhancementofaweakgrating,butoneneedsaphase-andgratingindexnpsz,tdcanbestudiedthroughtheconj