Li Jie, Li Jitao, Zheng Chenglong, Yang Yue, Yue Zhen, Hao Xuanruo, Zhao Hongliang, Li Fuyu, Tang Tingting, Wu Liang, Li Jining, Zhang Yating, Yao Jianquan
Opt Express. 2021 Aug 30;29(18):28329-28337. doi: 10.1364/OE.430033.
It is difficult for single-layer metal metasurfaces to excite in-plane component of magnetic dipole moment, so achieving giant intrinsic optical chirality remains challenging. Fortunately, displacement current in dielectric metasurfaces can form the in-plane magnetic moment which is not orthogonal to the electric dipole moment and forms intrinsic chirality. Here, we show a lossless all-silicon metasurface which achieves giant intrinsic chirality in terahertz band. The leaky waveguide mode in the chiral silicon pillars simultaneously excite the in-plane electric and magnetic dipole moments, which triggers the spin-selected backward electromagnetic radiation, and then realizes the chiral response. The theoretical value of circular dichroism in the transmission spectrum reaches 69.4%, and the measured one is 43%. Based on the photoconductivity effect of the silicon metasurface, we demonstrate optical modulation of the intrinsic chirality using near-infrared continuous wave. In addition, by arranging the two kinds of meta-atoms which are enantiomers, we show the spin-dependent and tunable near-field image display. This simple-prepared all-silicon metasurface provides a new idea for the design of terahertz chiral meta-devices, and it is expected to be applied in the fields of terahertz polarization imaging or spectral detection.
单层金属超表面很难激发磁偶极矩的面内分量，因此实现巨大的本征光学手性仍然具有挑战性。幸运的是，介质超表面中的位移电流可以形成与电偶极矩不垂直的面内磁矩，并形成本征手性。在此，我们展示了一种在太赫兹波段实现巨大本征手性的无损全硅超表面。手性硅柱中的泄漏波导模式同时激发面内电偶极矩和磁偶极矩，触发自旋选择的反向电磁辐射，进而实现手性响应。透射光谱中圆二色性的理论值达到69.4%，测量值为43%。基于硅超表面的光电导效应，我们展示了利用近红外连续波对本征手性进行光学调制。此外，通过排列两种对映体的超原子，我们展示了自旋相关且可调谐的近场图像显示。这种制备简单的全硅超表面为太赫兹手性超器件的设计提供了新思路，有望应用于太赫兹偏振成像或光谱探测领域。
