Study On Terahertz Wave Control Devices Based On VO₂ Tunable Metamaterial

The commercial era of the fifth generation?5G?mobile communication system has just began,many developed countries have started the research of the sixth generation?6G?communication technology.The working frequency of 6G communication has entered the terahertz frequency band,but the relevant functional devices of the terahertz frequency band are not mature enough,and there is still a long way to go before the practical and commercial application.Therefore,it is of strategic significance for the 6G communication to develop functional devices that can effectively transmit and regulate terahertz waves.Based on the phase change characteristics of vanadium dioxide?VO₂?,some tunable terahertz metamaterials are studied in this paper.The main contents are as follows:1.A tunable terahertz asymmetric transmission device based on VO₂material is proposed,the performance of the device is simulated by using the finite intergration technology?FIT?.The results show that the asymmetric transmission and polarization conversion of linearly polarized wave can be dynamically controlled in the range of 1.0-1.6THz.When the VO₂changes from the medium state to the metal state,The device has the following characteristics:?1?the asymmetric transmission parameter?can be modulated from 0 to 0.63;?2?For the forward transmission,the bandwidth with the polarization conversion ratio above 0.9 broadens from 0.05 THz to 0.6 THz;?3?For the backward transmission,the polarization conversion ratio is reduced from about 0.9 to 0.1.The mechanism is explained by combining the asymmetric transmission theory,the multiple reflection interference theory and electromagnetic coupling.2.A terahertz bandstop-bandpass converter based on VO₂is proposed.Firstly,the electromagnetic response of the device is studied at TE mode?the y-polarized waves?,and the experimental and simulational results show that the switching from bandstop to bandpass filter by changing the conductivity of VO₂in the range of 0.1-1.2 THz.The transformation principle is explained by combining the surface current distribution and the LC equivalent circuit model,and the control variable method is used to analyezed the influence of some key geometric parameters on the resonance frequency.Then,under the TM mode?x-polarized waves?,the change mechanism of resonance mode is studied.The results show that the change of resonance mode is due to the conductance coupling caused by gaskets phase transition.3.Two kinds of tunable terahertz modulators based on VO₂are proposed,which are labled as metasurface Y and X.The metasurface Y is mainly used to modulate the y-polarized waves,and the experiment and simulation results show that the resonance valley A?at 0.33 THz?and B?at 0.83 THz?of the metasurface Y can be merged into the resonance valley C?at 0.58 THz?by changing the conductivity of the gasket in the range of0.1 THz to 1.0 THz,which can be described by means of the dipole theory.In addition,the maximum modulation depth of transmission amplitude at 0.58 THz is up to 82.4%.The metasurface X is used to modulate the x-polarized waves,the experimental results show that the resonance frequency shows a red shift from 0.86 THz to 0.6 THz by changing the conductivity of the gaskets,and the phase modulation amplitude reaches 50°at 0.75 THz,where the transmission amplitude keeps constant.These proposed terahertz wave modulators based on VO₂tunable metamaterials are very important for the development of tunable terahertz functional devices.