基于超材料复合结构的太赫兹液晶移相器

Terahertz liquid crystal phase shifter based on metamaterial composite structure

为了解决现存太赫兹移相器的损耗较大且不可控、相移量较小的问题,本文设计了一种简易超材料复合结构实现的太赫兹移相器.该器件由4层结构组成,自上而下依次为L型金属谐振层、液晶层、弓型金属层、石英基底层.通过在上、下金属层施加偏置电压,改变液晶盒内液晶分子指向矢的偏转角α,从而改变液晶的有效折射率,器件的相位也随之发生变化,进而实现动态调控相位的目的.仿真结果表明:设计的太赫兹液晶移相器在1.68-1.78 THz间透射率可达0.968,插入损耗低至0.3 dB;当频率为1.7396 THz时,其最大相移为352.625°,在1.7315-1.7396 THz (带宽为8.1 GHz)频率内相移量超过352°.这种简易超材料多层结构为调控太赫兹波提供了一种新方法,在太赫兹成像、传感等领域有广泛的应用前景.

In order to solve the problems of large,uncontrollable insertion loss and small phase shift of the existing terahertz phase shifters,in this work a kind of terahertz phase shifter realized by a simple metamaterial composite structure is designed.The device is composed of four layers in structure,they from top to bottom,being an L-shaped metal resonance layer,a liquid crystal layer,a bow-shaped metal layer,and a quartz substrate layer.By applying a bias voltage to the upper metal layer and the lower metal layer,the deflection angle a of the director of liquid crystal molecules in the liquid crystal cell is changed,so that the effective refractive index of the liquid crystal changes,and the phase of the device also changes accordingly,thereby achieving the purpose of dynamic phase control.The performances of the upper metal layer,the lower metal layer and liquid crystal layer are optimized and compared with each other.The performance characteristics of the phase shifter under different values of deflection angle a and different values of incident angle θ are analyzed by frequency domain finite integration method.Through the simulation optimization and comparison of the size of the upper and lower metal layers and the thickness of the liquid crystal layer,the optimum is obtained.The simulation results show that the transmittance of the terahertz liquid crystal phase shifter can reach 0.968 in a frequency between 1.68-1.78 THz,and the insertion loss can be as low as 0.3 dB.When the frequency is 1.7396 THz,the maximum phase shift of the terahertz phase shifter is 352.625°.The phase shift exceeds 352° in a frequency range of 1.7315-1.7396 THz(Bandwidth is 8.1 GHz).This simple metamaterial multilayer structure provides a new method of controlling terahertz waves,and has broad application prospects in terahertz imaging,sensing and other fields.