Dynamic terahertz anisotropy and chirality enhancement in liquid-crystal anisotropic dielectric metasurfaces

To enhance and actively control terahertz (THz) anisotropy and chirality, we have designed and fabricated a THz composite device with a liquid crystal (LC) layer and Si anisotropic metasurface. By initial anchoring and electrically rotating the spatial orientation of the LC optical axis, the different symmetry relationships are obtained in this hybrid device. When the optical axis of LC is parallel or perpendicular to the optical axis of the Si metasurface, the anisotropy of the device will be enhanced or offset, which leads to a tunable phase-shift range of more than 180 degrees. When there is an angle between the two optical axes, due to the destruction of the mirror symmetry in the LC-Si anisotropic medium, the highest circular dichroism of the device reaches 30 dB in the middle orientation state of the LC optical axis, and the active modulation can be realized by changing the bias electric field on the LC layer. This composite device demonstrates rich characteristics for the feasible manipulation of THz polarization conversion and chiral transmission, which can be applied in THz polarization imaging and chiral spectroscopy. (C) 2022 Chinese Laser Press

Automated summary

To enhance and actively control terahertz anisotropy and chirality, a THz composite device consisting of a liquid crystal layer and an anisotropic metasurface has been designed and fabricated. By manipulating the spatial orientation of the liquid crystal optical axis, the device exhibits enhanced or offset anisotropy and tunable phase-shift range. The destruction of mirror symmetry in the LC-Si anisotropic medium enables active modulation and achieves high circular dichroism. This composite device demonstrates potential applications in THz polarization conversion and chiral transmission.