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1、APPLIEDPHYSICSLETTERS94,1135052009Reductionofphononresonantterahertzwaveabsorptioninphotoconductiveswitchesusingepitaxiallayertransfer11221,aS.Kasai,T.Katagiri,J.Takayanagi,K.Kawase,andT.Ouchi1CorporateR&DHeadquarters,CanonInc.,30-2Shimomaruko3-Chome,Ohta-ku
2、,Tokyo145-8501,Japan2EcoTopiaScienceInstitute,NagoyaUniversity,Furo-cho,Chikusa-ku,Nagoya464-8603,JapanReceived6February2009;accepted26February2009;publishedonline18March2009Abroadbandterahertztime-domainspectroscopyTDSsystemforfrequenciesofupto15THz,includ
3、ingthephononresonancefrequencyrange,hasbeendevelopedusingatransferredthin-ÞlmphotoconductiveswitchPCSdetector.Thethin-ÞlmPCSs,basedonlow-temperature-grownGaAs,werefabricatedusingepitaxiallayertransferontohigh-resistivitySisubstrates.Weobservedareductionofphon
4、onresonantabsorption,includingbetween7and10THz,inaforwardradiationconÞguration.Numericallycalculatedabsorptionspectrashowgoodagreementwithourexperimentalresults.Thistechniquewillprovidecompact,broadbandTDSsystems.©2009AmericanInstituteofPhysics.DOI:10.1063/1.3
5、103278Thegenerationanddetectionofultrabroadbandterahertzdown,andtheGaAssubstratewasremovedbyselective1Ð10pulseshavebeenstudiedusingvariousapproaches.Gen-wetetching.TheexposedLT-GaAsthinÞlmwasbondedtoerationbyopticalrectiÞcationanddetectionbyelectro-opticaSisub
6、strateusingepoxy-basedadhesivethicknessof1Ð3samplingusingnonlinearcrystalsaretypicalmethods.60Ð70m.Finally,theglasssubstrateandwaxwerere-4,5PhotoconductiveswitchesPCSsareemployedasemittersmovedbysolvent.6,7anddetectors.Usinglaser-inducedplasmaisanewlyde-F
7、igure2showstheexperimentalsetupoftheterahertz-velopedmethodcoveringthefrequencyrangebetween0.2TDSmeasurementsystem.Thebroadbandterahertzemitter8wastheorganiccrystal4-N,N-dimethylamino-4N-and12THz.However,ahigh-powertypicallyabove100mWexcitationlaserisnecess
8、arytogenerateterahertzpulsesmethyl-stilbazoliumtosylateDASTwith1.55mÞber10byopticalrectiÞcation.Furthermore,aregenerativeampliÞerlaser-basedultrashort-pulseirradiation.As