Research On Tunable Graphene-Based Terahertz Wave Devices

In recent years,the great breakthrough of the terahertz radiation source and the terahertz electromagnetic wave detection technology makes the research of terahertz wave related devices become the latest hot spot.Graphene is an excellent two-dimensional material with high electronic and crystal qualities,the tunable conductivity,terahertz bandgaps,and plasma oscillation make it an ideal material for tunable terahertz wave devices.Terahertz filter based on graphene cavity structure,terahertz switch based on graphene circular ring structure,terahertz switch based on graphene split-ring resonator array structure,terahertz power splitter based on graphene ribbon structure are investigated and analyzed in this paper.The main research work are as follows:1.Tunable terahertz wave filter based on graphene cavity structure is designed.The filter is composed of Si substrate,SiO2 layer,rectangular graphene ribbon and four square graphene sheets.We can alternate the chemical potential of four square graphene sheets to control the terahertz wave's transmission.The simulated results suggested that when the chemical potential of four square graphene sheets changes from 0.04 eV to 0.12 eV,the terahertz wave's transmission alters from 0.002 to 0.930 at 6THz.The filter's quality factor at 6THz is 1714 and the switching response time is 5.0ms.2.Terahertz wave switch based on graphene circular ring structure is designed.The switch consists of three graphene circular ring,two graphene ribbons and the polymethyl-methacrylate material.By tuning the chemical potential of middle graphene circular ring,the switch can realize the on-off control of the terahertz wave.The analyzed results suggested that when the chemical potential of middle graphene circular ring changes from 0eV to 0.2eV,the switch's extinction ratio alters from 0.59 dB to 26.99 dB at 7THz,the transmission response time of this switch is 1.23 ms.3.Terahertz wave switch based on graphene split-ring resonator array structure is designed.The switch is composed of three graphene split-ring resonators and one graphene ribbon,and all of them are embedded in a host dielectric medium polymethyl-methacrylate.By means of alternating the chemical potential of three graphene split-ring resonators,we can realize the on-off control of terahertz wave.The simulated results suggested that when the chemical potential of graphene split-ring resonator changes from 0.1eV to 0.2eV,the terahertz wave's extinction ratio alters from 30 dB to 1dB at 9THz,the transmission response time is 1.91 ms.4 Tunable terahertz wave power splitter based on graphene ribbon structure is designed.It is composed of five graphene ribbons embedded in the polymethyl-methacrylate.The terahertz wave is inputted from the left graphene ribbon,through the coupling effect between the graphene ribbons,it exports from two output ports eventually.By means of tuning the chemical potential of two middle graphene ribbons,the power splitter is able to achieve the specific terahertz wave energy distribution ratio of the output port 1 and the output port 2.When the frequency is 7THz,the simulated results suggested that when ?c1=0eV,?c2=0eV,the terahertz wave transmission ratio of output port1 and output port2 is 1 to 1;When ?c1=0.035 eV,?c2=0eV,the terahertz wave transmission ratio of output port1 and output port2 is 1 to 3;All of the terahertz wave export from the output port2,when ?c1=0.1eV,?c2=0eV;When ?c1=0eV,?c2=0.1eV,all of the terahertz wave export from the output port 1.The filter's isolation ratio is up to 39.86 d B and the transmission response time is 2.1ms.