Research On Terahertz Metamaterial Sensing And Modulation Characteristics Based On Graphene Plasmon-Induced Transparency

In the terahertz band,most biomolecules will produce their own unique characteristic information spectrum.This fingerprint spectrum characteristic makes terahertz spectroscopy more advantageous than traditional sensing technology.However,the terahertz wave cannot fully interact with the analytes when detecting low-concentration substances,negatively affecting the application of terahertz detection technology in sensing.As a non-natural artificial material,metamaterials are extremely sensitive to changes in the physical properties of the surrounding environment.Therefore,more and more metamaterials are applied to the sensing field in the terahertz band.However,traditional metamaterials composed of metals can only achieve static regulation.In contrast,graphene metamaterials can achieve dynamic regulation by changing their Fermi level,which closely connects sensing and modulation,greatly broadening the application range of metamaterials.Based on this,in this article,three tunable terahertz metamaterial sensors are designed with graphene metamaterials.The main research contents of this dissertation are as follows:1.To break through the single function of existing metamaterial sensors,this dissertation proposes a graphene multifunctional metamaterial sensor that combines the modulation function with the sensing function.The graphene pattern layer of the sensor is composed of a graphene band and a graphene semicircle.When the incident wave propagates along the y-polarization direction,the sensor will excite the plasmon-induced transparency（PIT）phenomenon in the 2.5～4.0 THz band through the bright-dark mode coupling.In addition,the sensor can not only achieve dual-mode regulation but also effectively modulate the transparent window by adjusting the carrier mobility of graphene.Finally,the results show that the sensitivity and FOM（Figure Of Merit）of the sensor can reach 1.4 THz/RIU（Refractive Index Unit）and 17.30 RIU^-1,respectively.2.Since the existing metamaterial sensor can only achieve a single PIT phenomenon in the single-polarization direction if the resonance modes of different analytes are similar in the same frequency band,it cannot effectively distinguish the analyte.Based on this,this dissertation proposes a graphene terahertz metamaterial sensor that can realize the dual-PIT phenomenon in two different polarization directions.The sensor generates two transparent windows in two different polarization directions through destructive interference between bright mode and quasi-dark modes.In addition to the tunability of the graphene,the sensor can also realize the conversion function of the two transparent windows between low frequency and high frequency by adjusting the polarization direction of the incident wave.In addition,the transmission spectrum of the sensor is not greatly affected at different incident angles.The results show that the sensitivity of the sensor can achieve 1.1 THz/RIU.3.To break through the low detection sensitivity of existing metamaterial sensors,this dissertation designs a graphene terahertz metamaterial sensor based on a continuous dielectric column.Its unit structure is composed of simple graphene rings and graphene strips.In the x-polarization direction,the three resonant units generate two transparent windows in the 1.5～2.5 THz band through the bright-quasi-dark coupling mode.At the same time,we introduce a new structure of continuous dielectric column to increase the contact range between the analyte and the sensor.And the comparative experiment shows that the introduction of a continuous dielectric column significantly improves the detection sensitivity of the sensor.Finally,the results show that the maximum detection sensitivity of the sensor can reach 1.2 THz/RIU.