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1、TerahertzactivespatialfilteringthroughopticallytunablehyperbolicmetamaterialsCarloRizza,1,2AlessandroCiattoni,2,a)ElisaSpinozzi,3andLorenzoColumbo1,41)DipartimentodiScienzaeAltaTecnologia,Universit`adell’Insubria,ViaValleggio11,22100Como,Italy2)ConsiglioNazionaledelleRicerche,
2、CNR-SPIN,67100CoppitoL’Aquila,Italy3)UniversityofRome“LaSapienza”,DepartmentofInformationEngineeringElectronicsandTelecommunications,ViaEudossiana18,00184Roma,Italy4)ConsiglioNazionaledelleRicerche,CNR-IFN,70126Bari,ItalyWetheoreticallyconsiderinfrared-drivenhyperbolicmetamat
3、erialsabletospatiallyfilteringterahertzradia-tion.Themetamaterialisaslabmadeofalternatingsemiconductoranddielectriclayerswhosehomogenizeduniaxialresponse,atterahertzfrequencies,showsprincipalpermittivitiesofdifferentsigns.Thegapprovidedbymetamaterialhyperbolicdispersionallowsth
4、eslabtostopspatialfrequencieswithinabandwidthtunablebychangingtheinfraredradiationintensity.Wenumericallyprovethedevicefunctionalitybyresortingtofullwavesimulationcoupledtothedynamicsofchargecarriesphotoexcitedbyinfraredradiationinsemiconductorlayers.Manipulatingterahertz(THz
5、)radiationisgenerallyadifficulttasksincethemostofstandardmaterialssimplydonotrespondtosuchfrequencies.However,theadventofmetamaterialshasallowedtopartiallyreducethisdif-ficultysincetheirelectromagneticpropertiescanbearti-ficiallymanipulated1throughasuitabledesignoftheun-derlyingc
6、onstituentunitcells.Atthesametimeanum-berofsetupshavebeenproposedforsteeringtheTHzradiation2andreconfigurableelectrically3oroptically4,5drivenmetamaterialshavebeenexploitedforconceivingactiveTHzdevices6.FIG.1.(Coloronline)LayeredmetamaterialsetuptogetherThemostoftheproposedact
7、iveTHzdevicesaretun-withTHz(TH)andinfrared(IR)planewavesgeometry.ablefrequency-domainfilterssinceitisrelativelysim-pletocontrolthemetamaterialdispersionpropertiesthroughexternalstimuli.InthisLetterwetheoreticallymagnetic(TMorp-polarized)monochromaticplaneim-proposeawayforachie
8、vingactiveandspatialfilteringpingingwithincidenceangleθontotheinterfa