Terahertz liquid crystal phase shifter based on metamaterial composite structure

Abstract

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 <i>α</i> 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 <i>α</i> and different values of incident angle <i>θ</i> 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.