A Research On Dynamic Terahertz Beam Steering Array Based On Vanadium Dioxide Metasurface

The terahertz wave is located between microwave band and infrared band in the electromagnetic spectrum.This special frequency range makes it have some unique properties.These properties make it more and more popular in nondestructive testing and sensing,high-speed wireless communication,etc.To better apply terahertz wave technology to these aspects,more mature terahertz modulation devices are needed.However,most natural materials do not respond to terahertz waves.The emergence of metametamaterial and metasurface provides a new way to solve this problem.Vanadium dioxide?VO₂?is a phase change material that can achieve conductivity changes of 2-5orders of magnitude under external excitation.It can undergo reversible state transition between the metallic and insulating state.When the tuned material is introduced into the metasurface structure,the dynamic modulation of the terahertz beam can be further realized,and its insertion loss is smaller.Therefore,this thesis uses VO₂ thin film to design dynamic terahertz beam control device to solve the above problems.First of all,in this thesis,CST electromagnetic simulation software is used to design,optimize and fabricate two dynamic terahertz wave control devices based on VO₂ coded metasurface,and the whole work is based on the principle of electromagnetic coded metasurface.These two metasurface control devices can dynamically control the number and direction of terahertz beams.In order to test its performance,the THz-TDS was used to test the reflectance/transmittance of the two prepared devices,and a beam control test system was set up to test its beam control performance.The dynamic terahertz wave beamsplitter designed and fabricated in this thesis can reflect the electromagnetic wave near 0.34THz at room temperature to more than 90%.Due to the presence of the back metal film,the incident wave is specularly reflected with high reflection efficiency and low loss.After the VO₂ changes to a metallic state,the normally incident 0.34THz electromagnetic wave is divided into two beams with approximately equal energy and a reflection angle of 33°,thereby realizing the switch between the single beam and dual beam reflection functions.The two-way dynamic terahertz beam control device designed and fabricated in this thesis maintains the transmittance of electromagnetic waves in the range of0.2¹THz at room temperature above 70%.After the VO₂ phase changes,the device function is transformed into a reflected beam splitter,which can split the normally incident 0.34THz electromagnetic wave into two beams with approximately equal energy and a reflection angle of around 33°,thereby realizing two-way dynamic modulation of terahertz waves.The two devices provide new ideas for the development of beam steering devices for terahertz communications.