非对称量子阱结构中非线性光学性质与其应用的分析

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1、产^一■●^’■ABSTRACTTHz-wavehasgoodperspective，securityandhighspectralresolution．Overthelastdecade，THz．wavehasbeenwidelyusedinbiology,medicineandcommunicationfields，whichhasgreatscientificvalueandbroadapplicationprospects．NowmanymethodshavebeenemployedtoobtaintheTHzradiationincludinge

2、lectronicsandphotonicsmethods，amongwhichthedifference—frequencygeneration(DEG)ofTHz．wavebasedonthenonlinearopticalfrequencymixinghasattractedgreatinterestforitsnumerousadvantages，suchasoperatingatroomtemperature，widelytunablerange，hi曲peakpower,lowcostandcompactness．Crystalscommonl

3、yusedhavesmallsecond-ordernonlineardifference—frequencycoefficients，whichinduceverylowconversionefficiency．Butasymmetricquantumwellshaveverylargesecond．ordernonlinearcoefficientsandtheirmagnitudearegenerallymicronspervolt．Usingasymmetricquantumwellsasthedifference-frequencygenerat

4、ioncrystalwillgreatlyimprovethepoorconversionefficiency．Therefore，theapplicationofasymmetricquantumwellinthedifference—frequencygenerationhasagreatpotential．Inthispaper,linear,second—orderandthird·ordernonlineareffectsinaspecialGaAs／A1GaAsquantumwellwereinvestigated．Furthermore，th

5、euseofquantumwelltogeneratecoherent他-waveviadifference-frequencygenerationWasmainlyexamined，andtheTHz．wavemodulationdevicesforpracticalapplicationswerestudied．Themaincontentsandthecreativepointsareasfollows：1．Basedontheladder-typeasymmetricquantumwell(AQW)，energylevels，wavefunctio

6、nsandopticalnonlineareffectsoftheasymmetricquantumwelltakinginto．accounttheeffectofconduction—bandnonparabolicitywerediscussed．Thesecond．ordernonlinearcoefficientoftheasymmetricquantumwelltakingintoaccounttheeffectofconduction-bandnonparabolicityWascalculatedandthenumericalresults

7、werepresentedfortypicalGaAs／AIo．2Gao．sAs／AIo．5Gao．5Asasymmetricquantumwell．WhenthequantumwellwidthLIequals70EgyptandL2equals300Egypt,theopficaldifference-frequencycoefficientz‰．雕isupto2．5019／man(higherthanGaAscrystal’Sopticaldifference—frequencycoefficientbyabout5ordersofmagnitude

8、)，andtheopticalrectificationcoeff