实验一普克尔效应实验目的验证偏振光中的普克尔效应测量普克尔单元的半波电压实验概述当自然光射到一些特殊的晶体表面时，会被分解成两束光，一束叫寻常光（o光），符合普通的折射定律，另一束则不符合，叫非常光（e光）。其折射率no和ne合称为晶体的主折射率。LiNbO3在强电场作用下能够变成双折射物质，由于o光、e光在晶体内的速度不同，通过晶体后，两光间产生相位差。进而在屏幕上出现干涉图样。改变电压值，干涉图样中的双曲线系会通过中心移向另外的线系。实验原理ThePockelseffectisthenamegiventotheoccurrenceofbirefringenceandtothechangeinexistingbirefringencephenomenainanelectricfieldlinearlyproportionaltotheelectricfieldstrength.ItisrelatedtotheKerreffect,althoughinthelattercasethebirefringenceincreasesexponentiallywiththeelectricfieldstrength.Forreasonsofsymmetry,thePockelseffectcanonlyoccurincrystalswithnoinversioncenter,whereastheKerreffectcanoccurinallsubstances.Whenthedirectionofthelightbeamandtheopticalaxisofbirefringenceareperpendiculartoeachother,wecallthisa“transverseconfiguration”(seeFig.1).Theelectricfieldisappliedinthedirectionoftheopticalaxis.ForPockelscellsinthetransverseconfiguration,lithiumniobate(LiNbO3)ismostoftenused.Lithiumniobatecrystalsareopticallyuniaxial,negativelybirefringentandhavethemainrefractiveindexesno=2.29fortheordinarybeam,andne=2.20fortheextraordinarybeam(measuredusingthewavelengthoftheHe-Nelaser,l=632.8nm.BirefringenceinaconoscopicbeampathTheproofofbirefringenceinaconoscopicbeampathisdescribedinnumerousopticstextbooks.Acrystalwithplaneparallelcutfacesisilluminatedwithadivergent,linearlypolarizedlightbeam,andthelightpassingthroughitisobservedbehindaperpendicularlyalignedanalyzer.Theopticalaxisofthebirefringenceisclearlyapparentintheinterferenceimage,asitisindicatedbythesymmetryinitsvicinity.Inthisexperiment,theopticalaxisisparalleltotheentranceandexitsurfaces;thisiswhytheinterferencepatternconsistsoftwosetsofhyperbolaswhicharerotatedby90withrespecttooneanother.Therealaxisofthefirsthyperbolasetisparalleltotheopticalaxis,whilethatofthesecondsetisperpendiculart...
