Study On Tunable Functional Devices Based On Dirac Semimetal

Metasurface has special properties different from traditional electromagnetic materials.It is a unique man-made two-dimensional periodic unit structure which has a broad application prospect because of its characteristics of easy integration and flexible control of terahertz wave.The materials used for designing metasurface devices have gradually evolved from traditional materials such as gold,copper,and dielectrics to two-dimensional new electromagnetic materials such as black phosphorus and graphene.Recently,the Dirac semimetal called "three-dimensional graphene" has been discovered due to its high electron mobility and used in the design and research of metasurface devices.The terahertz absorber is a very important part of the terahertz technology.Therefore,this paper uses the excellent characteristics of Dirac semimetal to design several absorbers based on the Dirac semimetal metasurface in the terahertz frequency band,and the absorption rate was calculated and their absorption mechanism was analyzed.In this paper,the tunable functional device based on Dirac semimetal metasurface is designed and researched using the CST Microwave Studio 2016 simulation software.The main contents include:1.We studied the principle of the metasurface and the analysis method of the absorber in depth,and analyzed the electromagnetic properties of the Dirac semimetal,including conductivity,dielectric constant,dispersion characteristics,etc.It provides a theoretical basis for functional device based on the Dirac semimetal metasurface,2.In the terahertz frequency band,a narrow-band single-frequency absorber based on the Dirac semimetal which can dynamically tunable in a wide band is designed.The research results show that the absorber can be dynamically adjusted in the range of 2.46THz to 3.50THz,and maintain perfect absorption.The quality factor is 29.8,which has the characteristics of incident angle and polarization insensitivity.We also discussed the effects of Dirac semimetal structure size and dielectric constant on the performance of single band absorber.By analyzing the electromagnetic field intensity,current distribution and magnetic field distribution at the resonant frequency of 2.98THz,the absorbing mechanism is revealed.In addition,for the absorption of TM mode and TE mode with different requirements,two polarization-sensitive wave absorbers are designed,which can achieve full absorption of TM waves or full absorption of TE waves at a single resonance frequency.3.Using the design of a single-band absorber,and the conclusion of the difference in resonance point at different sizes and the absorption peak superposition principle,a dualband and broadband absorber based on the Dirac semimetal metasurface was designed.The dual-frequency absorber is at 4.26Hz The absorption efficiency of the two frequency points of 5.34THz is more than 88%,and the Fermi energy level of the Dirac semimetal is adjusted so that it can be dynamically adjusted in the wide band range of the terahertz band;The broadband absorber can achieve 70% absorption efficiency between 4.78THz and 5.43THz.