Research On Novel Graphene Terahertz Devices

In recent years,with the rapid development of micro-nano fabrication technology,photoconductor technology and ultrafast laser technology,terahertz science and technology has gradually become a hot research focus in the world.One of the pivotal problems which influence the development of terahertz technology is the shortage of terahertz devices of high performance,so it is urgent to introduce a new material or new technology to design new types of terahertz devices to meet different application requirements.Graphene is a two-dimensional honeycombed structure crystal composed of a tightly packed single layer of carbon atoms.Since the graphene was discovered at the room temperature,it has obtained a lot of attention from researchers.Research results show that the conductivity of graphene under terahertz frequency can be controlled by the external bias voltage,and the plasma oscillation frequency of graphene is located in the terahertz band,the forbidden gap can just cover the terahertz band.Therefore,the design of terahertz devices by using graphene has great potential.At present,the research of graphene is still in the stage of theoretical research and experimental exploration,there are still some problems to be solved.A series of studies centering on graphene-based terahertz devices were carried out.Some problems in conventional terahertz devices,such as a wide range of frequency tuning,transmission loss and degree of integration,were discussed and investigated.And we designed a variety of graphene terahertz devices for different terahertz technology application.The main research results are as follows:1.It is the first time to propose that the graphene material can be applied to the design of planar electromagnetic band-gap structure.Five novel graphene terahertz planar electromagnetic band-gap structures were designed,and the equivalent circuit model parameters of three kinds of graphene terahertz electromagnetic band-gap structure were extracted.The influence of structure parameters and the chemical potential of graphene on the transmission characteristics were analyzed.The designed electromagnetic band-gap structure of graphene can effectively improve the tunable characteristics of terahertz electromagnetic band-gap,and can reduce the backward radiation of terahertz electromagnetic band-gap structure.2.It is the first time to propose the concept of graphene terahertz substrate integrated waveguide,and a detailed analysis of the transmission characteristics equations of the waveguide are carried out.The designed graphene substrate integrated waveguide had the features of single-mode transmission,low leakage loss,dynamic adjustment of cut-off frequency,which provided a new platform for the design of active terahertz substrate integrated waveguide devices.3.A terahertz substrate integrated waveguide antenna based on graphene stack was designed.The design method of the antenna was studied,and the influence of structure parameters on its performance was analyzed.The designed terahertz antenna not only had the advantage of the conventional metal cavity-backed antenna,but also had the characteristics of high integration degree,bandwidth,dual band and reconfiguration.4.A terahertz metamaterial absorber based on the graphene stack was designed.The mechanism of the adjustable absorbing of the absorber was explained theoretically,and the influence of structure parameters on absorbing performance was analyzed.Compared with the conventional terahertz absorber,the designed graphene absorber can have four kinds of features: ultra wide band,ultra-thin,highly efficient absorption,dynamic controllability.At the same time,the absorber was not sensitive to the polarization of the incident electromagnetic wave,it also can achieve the wide angle absorption.The research of this paper,not only solved some problems met during the design of conventional terahertz device,but also expanded the design ideas of graphene terahertz device,laying a basis for further study.