相变材料与超表面复合结构太赫兹移相器

Terahertz phase shifter based on phase change materialmetasurface composite structure

利用相变材料嵌入超表面组成复合结构实现太赫兹移相器,该器件自上而下依次为二氧化钒嵌入金属层、液晶、二氧化钒嵌入金属层、二氧化硅层.通过二氧化钒的相变特性和液晶的双折率特性同时作用实现对器件相位调控.随着外加温度变化二氧化钒电导率发生改变,器件的相位随之产生移动,同样的对液晶层施加不同的电压导致液晶折射率发生变化,器件相位也会有影响.经过这两种介质共同作用,最终实现对太赫兹波相位有效调控.仿真结果验证了该相移器在频率f=0.736 THz时,太赫兹移相器的最大相移量达到355.37°,在0.731—0.752 THz(带宽为22 GHz)频率范围相移量超过350°.这种基于相变材料与超表面复合结构为灵活调控太赫兹波提供了一种新思路,将在太赫兹成像、通信等领域有着广泛的应用前景.

With its rapid development,the terahertz technology is widely used in radar,imaging,remote sensing and data communication.As one of terahertz wave devices,the terahertz phase shifter has become a research hotspot.The existing phase shifters have the disadvantages of large volume,high power consumption and small phase shifting.In the present work,a tunable terahertz phase shifter with liquid crystal and vanadium dioxide is proposed.It is composed of an upper vanadium dioxide embedded metal layer,a liquid crystal,a lower vanadium dioxide embedded metal layer,and a silicon dioxide substrate in sequence from top to bottom.The liquid crystal is sandwiched between the upper and lower vanadium dioxide embedded metal layer.The phase of the device can be controlled by both the phase transition characteristics of vanadium dioxide and the birefringence of liquid crystal.By changing the external applied temperature,the conductivity of vanadium dioxide is changed,and the phase of the device shifts accordingly.Likewise the refractive index of the liquid crystal changes under different externally applied voltages.Finally,the phase of the proposed device can be effectively controlled in a terahertz range by both externally applied temperature and voltage.The phase shift characteristics of the device are analyzed by using software CST studio.The results verify that the terahertz phase shifter can achieve a maximum phase shift of 355.37°at f=0.736 THz and a phase shift is larger than 350°in a range of 0.731–0.752 THz(bandwidth 22 GHz).Therefore,compared with the traditional phase shifter,this kind of phase change material-metasurface composite structure provides a new idea for flexibly manipulating the terahertz beam.And it is expected to be widely used in terahertz imaging,terahertz wireless and other fields.