Analysis Of Dirac Semimetal Based Terahertz Device And Its Electromagnetic Characteristics

Terahertz wave is one of the electromagnetic waves with the frequency range of 0.1-10 THz.In recent years,terahertz technology has shown significantly research value and wide application prospects in material detection,security inspection,military and wireless communications because terahertz waves have the advantages of very low photon energy,strong penetration and obvious characteristic absorption peak.However,it is difficult for traditional materials in nature to produce a strong electromagnetic response to terahertz waves.The development of terahertz technology and its practical application process are largely hindered due to the lack of related terahertz devices.The recently developed metamaterials not only can flexibly control electromagnetic waves,but also generate strong electromagnetic responses to terahertz waves,that undoubtedly provides precise design methods and effective implementation methods for terahertz functional devices.The adjustable Dirac semimetal has attracted wide attention due to its ultra-high electron mobility and flexible chemical doping tunability.This paper designs several terahertz wave absorbers and polarizers based on metals and Dirac semimetals.The contents of the work are as follows:(1)Two polarizer based on double-arc are designed.One is an ultra-wideband line-tocircular polarizer based on metallic materials.The polarizer converts linear polarized waves into right-handed circular polarized waves in the range of 0.59-1.38 THz,with a relative bandwidth of 80.2%.The other is a reconfigurable terahertz polarizer based on the Dirac semimetal.When the Fermi level of the Dirac semimetal is 30 me V,the polarizer reflects the incident y-polarized wave into circular polarized wave,when the Fermi energy level of the Dirac semimetal is 45 me V,the polarizer converts the incident y-polarized wave to the perpendicular x-polarized wave,and the relative bandwidth reaches 67%.(2)Two terahertz wave absorbers based on double-arc structure are designed.One of them is an ultra-wideband absorber based on metal materials,which is composed of a double-arc metal layer,a dielectric layer and a metal reflective layer,the role of the metal reflective layer is to prevent the transmission of electromagnetic waves.The results show that the absorption of the incident wave in the 0.59-1.31 THz band exceeds 93%,and the relative bandwidth reaches 76%.The other is an ultra-wideband tunable absorber based on Dirac semimetal,that achieves an absorption of more than 95% in the 0.73-1.46 THz band and a relative bandwidth of 67%.When the energy level is changed,the absorption band will shift accordingly,so that the absorption frequency can be dynamically adjusted within 0.6-1.7THz without changing the structure parameters of the absorber.Finally,the absorption mechanism is analyzed by using interference cancellation and impedance matching theory.