Design Of Metamaterials Terahertz Modulator Based On Electro-optical Properties Of Graphene

With the rapid development of terahertz technology,terahertz technology has made important achievements in the fields of biomedicine,sensing,molecular imaging,and wireless communications.However,in THz applications,many functional devices such as THz switches,modulators,filters,etc.are required to perform very well.Along with the in-depth study of metamaterials,a new window was opened for in-depth study of the above devices.Metamaterials can absorb THz waves with strong electromagnetic properties such as negative electromagnetic parameters and negative refractive indices,which are not available in natural materials,and provide potential for functional devices in the THz band.Graphene has an extremely fast Fermi velocity,ultra-high carrier mobility at normal temperature,photoelectric performance,good light transparency,and can simultaneously convert its carrier concentration by physical or chemical methods,at THz waves.Controllable interactions with graphene.Thus graphene exhibits an advantage in regulating terahertz waves.In view of the above research background,this paper designs a terahertz wave modulator by combining artificial metamaterials and new graphene materials,including the following contents:1.A multi-frequency dynamically adjustable terahertz metamaterial modulator structure based on patterned graphene is proposed.The graphene layer-dielectric layer-graphene layer is used to achieve active control of the number of resonance frequencies without changing the geometry.By giving different bias voltages to different graphene layers,different Fermi levels can be obtained to increase the resonance frequency from 2 to 4,and at the same time obtain a modulation depth of 95%.Changing the angle of incidence of the THz wave results in a substantially unaffected transmission characteristic of the modulator due to the high degree of symmetry of the structure.At the same time,the mechanism of active control and modulation of the number of resonance points is expounded by studying the surface current and internal electric field of the structure.2.A graphene-based terahertz plasma induced transparent metamaterial structure is proposed.The graphene elliptical ring distribution of the same four geometrical structures is composed of vertical and horizontal directions.Based on the light-dark mode theory,plasma-induced transparency is achieved by changing the Fermi level by applying different bias voltages to the horizontal elliptical ring and the vertical elliptical ring,respectively,without changing the structure size.The PIT(Plasmon Induced Transparency,PIT)window is controlled by changing the coupling distance between the graphene elliptical rings in the metamaterial structure.More importantly,by changing the graphene Fermi level,dynamic tuning of the resonant frequency of the transparent window can be actively controlled in the study frequency band,which has high applicability in practice.Simultaneously changing the graphene Fermi level can achieve wave modulation with a modulation depth close to 80%.Finally,a large group delay was observed by a change in the graphene Fermi level,which was 0.52 ps at the transparent peak.These results can be applied to tunable terahertz switches,slow-light devices,and modu ators.