Broadband Tunable Terahertz Absorber Based On Vanadium Dioxide Metamaterials

Nowadays,the application of terahertz technology is in the process of continuous development and research,and its broad scientific prospect has been widely recognized in the world.Compared with traditional electromagnetic materials,Metamaterials(MM)have the advantages of ultra-thin thickness and frequency selectivity and it can be easily designed.Absorber is an important functional device of metamaterials,which has aroused great interest in the field of metamaterials.Since Professor N.I Landy and other researchers proposed the theory of electromagnetic metamaterials perfect absorption,researchers begin to explore how to design the perfect absorber which is broadband and not sensitive for the polarization angle or incident angle.However,most of these absorbers have a functional limitation,that is,most absorber's electromagnetic absorption intensity is not tunable,once the device is finished,it's function is fixed.Therefore,in order to face the increasingly complex electromagnetic application environment,we need to design a kind of perfect absorber with tunable function.In this paper,the design principle of terahertz frequency electromagnetic metamaterial absorber is discussed in detail.The perfect absorber of broadband is designed by optimizing the structural parameters of superstructure to achieve impedance matching.On the basis of this,vanadium dioxide,is further introduced,and the transition from dielectric to metal state can be completed rapidly when temperature changes.By changing the environment temperature,the properties of vanadium dioxide,such as conductivity,the intensity of the absorption of electromagnetic absorber will be changed gradually,so the intensity of the broadband electromagnetic absorption is tunable.Therefore,on the basis of this,we put forward an electromagnetic absorber based on vanadium dioxide in terahertz.An active absorption device is proposed based on vanadium dioxide metamaterials.By controlling the conductivity of vanadium dioxide,resonant absorbers are designed to work at wide range of terahertz frequencies.Numerical results show that a broadband terahertz absorber with nearly 100%absorptance can be achieved,and its normalized bandwidth of 90%absorptance is 60%under normal incidence for both transverse-electric and transverse-magnetic polarizations when the conductivity of vanadium dioxide is equal to 2000?-1cm-1.Absorptance at peak frequencies can be continuously tuned from 30%to 100%by changing the conductivity from 10?-1cm-1 to 2000?-1cm-1..Absorptance spectra analysis shows a clear independence of polarization and incident angle.The presented results may have tunable spectral applications in sensor,detector,and the rmophotovoltaic device working at terahertz frequency bands.