Zeng Yali, Duan Qilin, Xu Jinying, Yang Zhilin, Chen Huanyang, Liu Yineng
Department of Physics and Institute of Electromagnetics and Acoustics, Xiamen University, Xiamen 361005, China.
Department of Physics, Fuzhou University, Fuzhou 350108, China.
iScience. 2023 Feb 2;26(3):106115. doi: 10.1016/j.isci.2023.106115. eCollection 2023 Mar 17.
Two-dimensional (2D) chirality-induced asymmetric transmission/reflection has great potential for polarization applications. Usually, asymmetric effects resulting from circular conversion dichroism (CCD) occur in chiral metasurfaces. Here, we propose a single-layer twisted graphene-patterned (with tilted elliptical hole arrays) metasurface and theoretically reveal its tunable CCD in the terahertz (THz) region. The unit cell of the metasurface is achiral. Merely by altering the in-plane orientation of holes for structural 2D chirality, a tunable CCD can be achieved at normal incidence. Interestingly, the reflection phase can be considered an intuitive method to show this metasurface's anisotropy, which complements the conventional CCD measurement in characterizing chiral materials. Furthermore, we can achieve active CCD based on the tunability of graphene. Due to the Fabry-Pérot resonance, a multiband enhancement of CCD spectrum will happen by changing the dielectric layer thickness. The proposed metasurface provides more flexible opportunities for designing active THz devices for polarization manipulation.
二维（2D）手性诱导的不对称透射/反射在偏振应用方面具有巨大潜力。通常，由圆转换二向色性（CCD）产生的不对称效应出现在手性超表面中。在此，我们提出一种单层扭曲石墨烯图案化（具有倾斜椭圆孔阵列）的超表面，并从理论上揭示其在太赫兹（THz）波段的可调谐CCD特性。该超表面的单元结构是非手性的。仅仅通过改变孔的面内取向以实现结构二维手性，就能在正入射时实现可调谐的CCD。有趣的是，反射相位可被视为展示该超表面各向异性的一种直观方法，它在表征手性材料方面对传统的CCD测量起到补充作用。此外，基于石墨烯的可调谐性，我们能够实现有源CCD。由于法布里 - 珀罗共振，通过改变介电层厚度会使CCD光谱出现多波段增强。所提出的超表面为设计用于偏振操纵的有源太赫兹器件提供了更灵活的机会。
