Design And Study Of Terahertz Wave Absorption Based On Adjustable Materials

Terahertz is a new kind of electromagnetic wave with many unique properties,and the terahertz technology has attracted much attention from researchers.In the past decade,electromagnetic metamaterial absorbers,which have obtained the excellent absorption properties such as polarization insensitivity and broadband,have developed rapidly.However,it is difficult to simultaneously tune the resonant frequencies of these absorbers and separately tune one of the frequencies unless changing the geometric parameters of the structures.Due to the resonance mechanism of metamaterials themselves,its performance is often fixed once the structure is proposed,which cannot meet the flexible wave-absorbing requirements under various scenarios.Therefore,it is necessary to add tunable materials to the structure.This paper mainly designs the terahertz absorbers made of two tunable materials: electrically tunable graphene and temperature tunable semiconductor material InSb.And then,the dual-frequency absorbers based on two tunable materials is designed by the finite-difference timedomain method to realizing simultaneous tuning of double resonant frequencies and separate tuning of each frequency:Based on the electrically tunable characteristics of graphene material and its surface plasmon characteristics in the terahertz band,the single-band and dual-band graphene disk tunable terahertz absorber are designed respectively.The single-band tunable absorber is consisting of a graphene disk,a medium and a metal,which can tune the resonance wavelength and absorption rate by setting different chemical potentials on graphene.The dual-band tunable absorber is consisting of two graphene disks,medium and metal,which can realize the tuning of dual resonance frequency and absorption rate.The absorption mechanism of the two absorbers can be explained by using the electromagnetic field and surface current distribution.The influences of disk radius,medium thickness and oblique incidence on absorption spectrum are aslo analyzed.By simultaneously setting different chemical potentials for the two graphene disks or one of them,the simultaneous tuning of the resonance frequency of the dualfrequency absorber structure and the separate tuning of each frequency are respectively realized.Based on the temperature-sensitive characteristics of indium antimonide(InSb),the InSb terahertz dual-frequency absorber is designed.Firstly,a single InSb cylindrical absorber is designed based on the characteristics.Then,a terahertz dual-frequency absorber composed of four InSb cylinders with different radii is designed,thus respectively realizing the impedance matching at two resonant frequencies.When the temperature of InSb is constant,nearly perfect absorption is realized under the condition of double frequency.And then,the absorption mechanism is further analyzed according to the electromagnetic field and surface current distribution obtained by simulation.Meanwhile,the influences of the structure parameters and incident angle of the absorber on absorption spectrum are also analyzed.According to the characteristics of temperature tunable of InSb,the simultaneous tuning of two resonance absorption frequencies and the separate tuning of each frequency are studied.Finally,a simple attempt is made to combine graphene with InSb material,which not only realizes the double tuning of electricity and temperature in structure,but also realizes the coarse and fine tuning of single resonance peak and the bandwidth tuning of multiple resonance peaks.