Research On Graphene Terahertz Detector And Metasurface Modulator

In the past two decades,the research of terahertz technology has developed rapidly.In order to meet the application requirements of terahertz waves,terahertz detectors and modulators have gradually become research hotspots.However,these two devices are still in short supply at present,mainly due to the weak response of most natural materials in the terahertz band,and the prepared devices also have many shortcomings,such as low response rate,slow modulation rate,and small modulation depth.The two-dimensional material graphene responds significantly to terahertz waves,graphene-based terahertz detectors and graphene metasurface modulators have great application potential.Firstly,this paper studied the energy band structure and modulation mechanism of graphene,and then studied the transfer process of graphene,and obtained a single-layer graphene film with good integrity.Then,a graphene field effect transistor（GFET）with Si O₂/Si substrate was designed.The micro-nano processing technology is used to prepare a GFET with good ohmic contact,and the modulation performance of graphene is tested and analyzed.Two types of terahertz detectors with single structure and array structure were prepared.The terahertz response currents were 0.12μA and 2.1μA respectively,which proved their response to terahertz waves.The response rates were Ri（single）≈60 m AW^-1,Ri（array）≈280m AW^-1.Based on the excellent electrical tunability of graphene,combined with the Fano resonance metasurface,which is highly sensitive to graphene conductivity,a terahertz modulator combining the two advantages is proposed.The Fano resonance at 0.45 THz is obtained through simulation and proved by adjusting the Fermi level of graphene,the Fano resonance can be significantly modulated,and the maximum modulation depth is 12.63%.A terahertz modulator with graphene combined with a metasurface structure was prepared experimentally,and the transmission spectra of 0.46 THz Fano resonance and 0.63 THz dipole resonance were obtained through terahertz spectroscopy system testing,which are in good agreement with the simulation results.Multiple sets of transmission spectra were measured by the external grid voltage,and the change of the peak value at the Fano resonance frequency at 0.46THz conforms to the modulation law produced by the change of graphene conductivity.The maximum modulation depth of 11.10%is obtained in the range of grid voltage 0～60 V.