Study On The Transmission Properties Of THz Modulated By Graphene Metamaterials

With the rapid development of science and technology,terahertz metamaterials have become more and more important.However,terahertz metamaterials have also exposed some of its limitations.The inability to implement a wide range of dynamic tunings largely limits the implementation and practical application of functional devices.Graphene has a very high electron mobility and a special band structure,and its conductivity changes very significantly under voltage excitation or laser excitation,so it is very suitable for modulating terahertz materials.Based on this,this paper uses graphene to prepare metamaterials and realizes dynamic tuning by voltage excitation and laser excitation.In this study,graphene films were prepared by CVD method which is easier to control film thickness and size.Single-layer graphene films were excited by different voltages to study the modulation effect of voltage-excited graphene on terahertz waves.The terahertz time domain waveform is tested and the terahertz transmission spectrum is calculated to analyze the modulation of the graphene terahertz transmission characteristics by the forward and reverse voltage excitations.It is concluded that the forward voltage increases the transmittance of graphene to the terahertz wave,and the reverse voltage decreases the transmittance of the terahertz wave.The overall modulation range is about 20%.The single-layer graphene film and multi-layer graphene film were pumped by 980 nm laser with no power,and the modulation effect of laser-excited graphene on terahertz wave was studied.The influence of film thickness on the modulation effect was tested.It is concluded that the transmission performance of graphene to terahertz decreases with the increase of pump light power,and the single-layer structure has a larger modulation range and higher sensitivity.The single-layer graphene has a modulation range of about 91%,and the multilayer has a thickness of about 47%.The metamaterial is prepared by a photolithography process or the like on a single-layer graphene film.The transmission characteristics of terahertz waves in TE and TM waves of graphene metamaterials and metamaterials were tested.It was found that graphene has a certain attenuation effect on the resonance amplitude of metamaterials.The terahertz time-domain waveforms of different voltage excitations of the graphene metamaterials under TE and TM waves were tested to calculate the terahertz transmittance spectrum.It is concluded that the transmittance decreases at the forward voltage and the transmittance increases at the reverse voltage,and the modulation range of nearly 20% is generally achieved and the amplitude of the resonance peak is always small,contrary to the effect of the graphene film.It is indicated that changing the carrier concentration by graphene voltage excitation has a modulation effect on the LC resonance of the metamaterial.