Research On Terahertz Tunable Absorbers Based On Vanadium Dioxide

Terahertz technology is a typical interdisciplinary frontier field,which provides a golden opportunity for the development of science and technology and social progress.It combines the characteristics of electronics and photonics,and is the latest science and technology foundation of the industry in the 21st century.At present,the lack of effective terahertz functional devices is one of the important factors limiting the development of terahertz technology.Terahertz metamaterial absorber is an important functional device,which has broad application prospects in terahertz imaging,sensing and stealth.However,once the existing terahertz metamaterial absorber is manufactured,it is difficult to change the absorption performance,resulting in the application range of the absorber is greatly limited.Vanadium dioxide(VO₂)is a kind of common phase change material,which can change from insulating state to metallic state near 68?.It is an ideal choice for terahertz tunable devices.This paper focuses on the research of vanadium dioxide terahertz tunable absorption devices.The main contents are as follows:1.The related theory of terahertz metamaterial absorber is studied,and the structural characteristics,phase transition mechanism,simulation modeling and fabrication method based on vanadium dioxide metamaterial absorber are also discussed.2.Two kinds of tunable narrow-band absorption devices based on vanadium dioxide are designed:Terahertz single frequency amplitude tunable narrow-band absorber and terahertz single-three frequency tunable narrow-band absorber.The terahertz single frequency amplitude tunable narrow-band absorber has been successfully fabricated and tested.(1)Terahertz single frequency amplitude tunable narrow-band absorber:the simulation results show that the absorptivity of 0.71 THz before VO₂phase transition is only 0.10,while after VO₂phase transition,the absorption is improved to 0.87,and the absorption modulation depth reaches 77%.In addition,the absorber sample was fabricated and tested.The test results show that the absorption rate of 0.71 THz before VO₂phase transition is almost consistent with the simulation results.Under the trigger current of 380m A,the absorption rate of 0.66 after VO₂phase transition,the modulation depth of the device is about 42%.(2)Terahertz single-three frequency tunable narrow-band absorber:in the transverse electric field(TE)mode,there is a single frequency perfect absorption of 0.93 at 0.79 THz before VO₂phase transition,while after VO₂phase transition,there is a triple frequency perfect absorption of over 0.93 at 0.38,0.79 and 1.1 THz at the same time.Therefore,by controlling the phase transition state of VO₂,the absorber can achieve perfect absorption of single frequency to three frequency with fast conversion.3.A tunable broadband absorption device based on vanadium dioxide is designed:a simple three-layer structure,which is composed of VO₂resonator in the top layer,polyimide(PI)gasket and metal substrate in the bottom layer.When VO₂transits from insulating state to metal state under external excitation,the absorption of the absorber increases from 0.03 to more than 0.9 in the frequency range of 0.70?1.70 THz,and the relative bandwidth is about 83%,the modulation depth is about 96%.The three kinds of vanadium dioxide terahertz tunable absorbers designed in this paper are of great significance for the effective control of terahertz wave.The research methods in this paper are of great reference value to promote the development of terahertz technology.