全介质超表面中的手性太赫兹响应

Chiral optical response of all–dielectric metasurface in terahertz band

摘要:

基于单层金属手性谐振器的超表面在垂直入射条件下很难激发较大的手性光学响应，难以形成与电偶极矩不正交的面内磁偶极矩分量。光场在介质超原子中激发的位移电流可能引发面内磁矩，进而实现高效的手性光学响应。基于无损的全硅超表面在太赫兹波段实现了巨大的手性响应。手性硅柱中的泄露波导模式同时激发了面内电偶和磁偶极矩，从而引发了自旋选择的后向电磁辐射，进而实现了太赫兹波的手性光学响应。利用线栅偏振片搭建了偏振相关的时域光谱测试系统，测得透射光谱中的圆二色性峰值达0.2。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的思路，有望应用于太赫兹偏振成像、光谱检测等领域。

Abstract:

It is difficult to excite large chiral optical responses for metasurfaces based on single-layer metal resonators under normal incidence, because they are difficult to excite in-plane magnetic dipole moment that are not orthogonal to the electric dipole moment. The displacement current excited by optical field in the dielectric meta-atoms may induce an in-plane magnetic moment to achieve chiral optical responses. A huge chiral response is achieved in terahertz band based on the lossless all-silicon metasurface. The leaky waveguide mode in the chiral silicon pillar excites the in-plane magnetic dipole moment, which triggers the spin-selected backward electromagnetic radiation, and then realizes the chiral optical response of terahertz wave. A polarization-dependent TDS system is built by using wire grid polarizers，and the peak value of circular dichroism in the transmission spectrum reaches 0.2. This simple-prepared all-silicon metasurface provides a new idea for the design of terahertz chiral metadevices, and it is expected to be applied in the fields of terahertz imaging and spectral detection.