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β-BBO晶体在THz波段二阶非线性极化系数的研究.docx

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β-BBO晶体在THz波段二阶非线性极化系数的研究 Abstract Inthisarticle,weinvestigatedthesecond-ordernon-linearpolarizationcoefficientofβ-BBOcrystalintheTHzregion.Theexperimentalresultsshowedthattheβ-BBOcrystalhasexcellentnon-linearopticalpropertiesintheTHzregion,whichmakesitapromisingcandidateforTHzwavegenerationanddetection.Wealsodiscussedthepossibleapplicationsofβ-BBOcrystalintheTHzregionandpointedoutthechallengesthatneedtobeovercomeinfutureresearch. Introduction Terahertz(THz)radiationhasattractedextensiveattentionduetoitspotentialapplicationsinvariousfields,suchasimaging,spectroscopy,communication,andsecurityscreening.However,thedevelopmentofTHztechnologyishinderedbythelackofefficientTHzsourcesanddetectors.Non-linearopticalmaterialshavebeenconsideredaspromisingcandidatesforTHzwavegenerationanddetectionduetotheirhighnon-linearsusceptibility. β-BaB2O4(β-BBO)isawidelyusednon-linearopticalmaterialinthevisibleandnear-infraredregionsduetoitsfavorableproperties,includinghighnon-linearsusceptibility,widetransparencyrange,andlowabsorptioncoefficient.However,itsnon-linearopticalpropertiesintheTHzregionhavenotbeenfullyinvestigated.Inthisarticle,wepresenttheexperimentalresultsofthesecond-ordernon-linearpolarizationcoefficientofβ-BBOcrystalintheTHzregionanddiscussitspotentialapplications. Experimentaldetails Theexperimentalsetupisshowninfigure1.Two-colorpump-probespectroscopywasusedtomeasurethesecond-ordernon-linearpolarizationcoefficient(χ(2))oftheβ-BBOcrystalintheTHzregion.ThepumpbeamwasgeneratedbyaTi:sapphirelaserwithacentralwavelengthof800nmandarepetitionrateof1kHz.TheprobebeamwasgeneratedbyaTHztime-domainspectroscopysystemwithabandwidthof0.3-3THz.Thetwobeamswerecollinearlyfocusedontheβ-BBOcrystalwithaspotsizeofabout1mm.TheTHzwavewaspolarizedperpendiculartothepumpbeampolarization.TheoutputTHzpulsewasdetectedbyaZnTecrystalandthenrecordedbyalock-inamplifier. TheTHz-TDSsystemusedfortheprobebeamwasbasedonafemtosecondTi:sapphirelaserwithanaveragepowerof1Wandarepetitionrateof80MHz.Thelaserpulseswer