激光光束的调制、传输与聚焦的分析

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1、华侨大学硕士学位论文AbstractInrecentyears,thestudyonthefieldofbeamstransimitingthroughtheturbidmediahasbeendrawnconsiderableattention.Thesparklyresultsinthisfieldarefocusingandimagingthroughtheturbidmedia.Randomscatteringcomesfrombeamstransimitingthroughmaterials,

2、suchaswhitepaint,milk,orhumantissueopaque.Inthesematerials,multiplescatteringandinterferencedistorttheincidentwavefrontsostronglythatallspatialcoherenceislost.Incidentcoherentlightdiffusesthroughthemediumandformsavolumespecklefieldthathasnocorrelationson

3、adistancelargerthanthewavelength.Throughthecompletedistortopticalfield,itcanmanagetofocusthespecklefieldbaseonamplitudespatiallightmodulationusingthewell-establishedwavefrontcorrectionmethodsofadaptiveoptics.Inthisthesis,wecarryoutastudyonmodulation,prop

4、agationandfocusingoflaserbeams.Includingthreeparts:1.Thetransmittanceoftightlyfocusedlinearpolarizationvortexbeamsandnon-vortexbeamsthroughturbidmediaisexperimentallymeasured.Thesimulationresultsfittheexperimentalresultsverywell.TheinfluencesoftheNAofobj

5、ectiveandthetopologicalchargeofvortexbeamsonthetransmittanceareinvestigatedingreatdetail.Itisshownthat,thetransmittanceisstrongerifbeamscarryspiralphase.Moreover,alargertopologicalchargeandalargerNAresultinastrongertransmittance.2.Byusingthewell-establis

6、hedwavefrontcorrectionmethodsofadaptiveoptics,wedemonstratethatwecanfocusthespecklefieldatparticularlocationbypre-modulatingthewavefrontofbeamsusingSLM(spatiallightmodulation).BycontrollingtheamplitudeoftheinputbeamsbychangingthegrayleveloftheSLMpixel,we

7、candecreasetheinfluenceofinterferencedistortoftheturbidmedium.Furthmore,wechangethedifferentfactorstorestraintheinfluenceofthebackgroundnoisetogetthebetterexperimentalresults.3.BasedonthetheorythatSiegmanproposedavariantoftheHGmodesthathereferredtoasthee

8、legantformoftheHermite-Gauss(eHG)beams.AnewkindofIIAbstractlasercavitymodeswasproposed.ThemainfeatureisthattheyshowasymmetrybetweentheargumentoftheGaussianfunctionandthatoftheHermitefunction.Furthermore,weintroducethefamil