Terahertz Band Stop Filtering Based On Graphene Magnetoplasmon

The unique electronic energy band structure of the two-dimensional material graphene provides it with good electromagnetic properties.Under the action of an external magnetic field,the conductivity and relative permittivity of graphene will change.Therefore,graphene has good magnetic tunability,which also makes graphene an ideal material for implementing active tunable plasma components.This paper mainly conducts detailed theoretical analysis and simulation calculations on the design of graphene single-frequency / dual-band broadband terahertz band-stop filters.The main research contents are as follows:The theoretical analysis method of graphene magnetic surface plasmon is introduced.The electromagnetic parameters of graphene are analyzed theoretically.The effect of graphene chemical potential on its electrical conductivity and relative dielectric constant is analyzed through numerical calculation results.In addition,the change of graphene conductivity in the presence of magnetic field was analyzed.A band stop filter with a symmetrical graphene magnetic surface plasma is designed.The structure of the filter is composed of two layers of graphene arrays,which are separated by a gallium arsenide substrate.The top graphene array and the bottom graphene array have the same two-dimensional array period.First,a theoretical analysis of the rectangular graphene array is carried out,and the relationship between the resonance peak position generated by the plasmon resonance on the graphene surface and the length L and width W of the rectangular graphene is discussed.The numerical calculation results show that for the square graphene array(ie L = W),the position of the resonance peak is related to the side length of the square graphene.Therefore,a reasonable design of the side length of the graphene in the two-layer(top and bottom)square graphene array can make the two resonance peaks merge into a stop band with a certain bandwidth.Secondly,the effects of graphene chemical potential and applied magnetic field on the stop band are analyzed.The analysis results show that the increase in the chemical potential causes the stop band to shift blue,and the presence of the magnetic field causes the originally overlapping stop band to move in the reverse direction.Finally,a tunable dual-frequency broadband band-stop filter based on graphene magnetic surface plasma is designed.After theoretical analysis and simulation calculations,the optimal size of the dual-band wideband band-stop filter with L1 = 107 nm,L2 = 106 nm,and P = 120 nm is obtained.The simulation results show that when the magnetic field B = 3 T,the bandwidths of the two stop bands formed by the reverse movement are respectively 0.2 THz and 0.225 THz,and the corresponding center frequencies of the two stop bands are 6.11 THz and 7.11 THz,respectively.The innovation of the design in this chapter lies in the separation of the coincidence stop band by applying an external magnetic field.A band-stop filter with asymmetric graphene magnetic surface plasma is designed.The structure of the filter is composed of the bottom copper film layer,the middle gallium arsenide base layer,and the top graphene array layer with defects.First,a graphene array model is constructed,and the difference between graphene surface plasmon resonance in a complete graphene array and a defective graphene array is discussed.The reason for the change of resonance peak in the two graphene array structures is analyzed.The results show that the plasmon resonance generated by the incident wave on the surface of the complete graphene is not affected by the polarization direction of the incident wave electric field,while the plasmon resonance generated by the incident wave on the surface of the defective graphene is affected by the polarization direction of the incident wave electric field..This phenomenon is caused by the change of the relative dielectric constant of the medium in the dispersion equation satisfied by the defect.Secondly,the effect of the side length of the defect and the distance between the centers of the two defects on the resonance frequency is studied.The simulation results show that as the side length of the defect and the distance between the centers of the two defects decrease,the distance between the two resonance peaks also continues to decrease.Therefore,the structure size can be reasonably designed so that the two resonance peaks form a certain bandwidth.Furthermore,the effects of graphene chemical potential and external static magnetic field on the stopband bandwidth are studied.The results show that the increase in the chemical potential causes a blue shift in the position of the stopband,but the stopband bandwidth does not change.The increase of the external magnetic field plays a certain role in adjusting the bandwidth of the stop band.Finally,a tunable single-frequency broadband band-stop filter based on graphene magnetic surface plasma is designed.Simulation results show that the magnetic field changes from 0 T to 0.5 T,the band-stop filter stop-band width changes from 0.09 THz to 0.12 THz,and the center frequency of the stop-band is5.70 THz.The innovation of the design in this chapter is to adjust the stopband bandwidth by applying an external static magnetic field.