实验报告大物理.pdfVIP

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n和n合称为晶体的主折射率。LiNbO3（铌酸锂））在强电场作

oe

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

幕上出现图样。改变电压值，图样中的双曲线系会通过移向另外的线系。

实验原理

ThePockelseffectisthenamegiventotheoccurrenceofbirefringenceandtothechangeinexisting

birefringencephenomenainanelectricfieldlinearlyproportionaltotheelectricfieldstrength.Itisrelatedto

theKerreffect,althoughinthelattercasethebirefringenceincreaseponentiallywiththeelectricfield

strength.Forreasonsofsymmetry,thePockelseffectcanonlyoccurincrystalswithnoinversioncenter,

whereastheKerreffectcanoccurinallsubstances.

Whenthedirectionofthelightbeamandtheoptical

axisofbirefringenceareperpendiculartoeachother,

wecallthisa“transverseconfiguration”(seeFig.1).

Theelectricfieldisappliedinthedirectionofthe

opticalaxis.ForPockelscellsinthetransverse

configuration,lithiumniobate(LiNbO3)ismostoften

used.·

Lithiumniobatecrystalsareopticallyuniaxial,

negativelybirefringentandhavethemainrefractiveindexesno=2.29fortheordinarybeam,andne=2.20

fortheextraordinarybeam(measuredusingthewavelengthoftheHe-Nelaser,l=632.8nm.

Birefringenceinaconoscopicbeampath

Theproofofbirefringenceinaconoscopicbeampathisdescribedinnumerousopticstextbooks.Acrystal

withplaneparallelcutfacesisilluminatedwithadivergent,linearlypolarizedlightbeam,andthelight

passingthroughitisobservedbehindaperpendicularlyalignedanalyzer.

Theopticalaxisofthebirefringenceisclearlyapparentinthe