Flexible Liquid Crystal Cascade Dielectric Metasurface for Dynamically Controlling Terahertz Beam Deflection

Abstract

Terahertz (THz) beam deflection devices with tunable capabilities are highly desired in future wireless communication and radar systems. In this work, a cascaded metadevice is constructed by integrating liquid crystal (LC) into a dielectric metasurface, and then the phase of each meta-atom is designed to achieve different polarization conversions and spatial phase gradient distributions. Therefore, by changing the polarization of the incident wave or the LC optical axis orientation, an active THz beam deflection device that can actively and independently control the spin state and deflection angle of the output wave can be obtained. Specifically, the output right circularly polarized (RCP) wave is deflected to the +1st diffraction order, and the output left circularly polarized (LCP) wave is deflected to the +2nd diffraction order. The experimental results indicate that the cascaded metadevice exhibits a large angular spatial dispersion in the frequency angle scanning range of +25°–+17.5° (+1st order) and +52.5°–+35° (+2nd order) corresponding to the broadband range of 0.6–0.83 THz. The spin isolation of all diffraction order channels can reach over 10 dB and the maximum diffraction efficiency of 56% can be obtained. In addition, the universality of the proposed LC-cascaded metasurface design concept has also been verified, providing a feasible path for complex, multifunctional, and active THz wavefront manipulation, thereby exploring more possible application scenarios.