Arbitrary terahertz chirality construction and flexible manipulation enabled by anisotropic liquid crystal coupled chiral metasurfaces

Abstract

Chiral metasurfaces integrated with active materials can dynamically control the chirality of electromagnetic waves, making them highly significant in physics, chemistry, and biology. Herein, we theoretically proposed a general and feasible design scheme to develop a chiral metadevice based on a bilayer anisotropic metasurface and a monolayer liquid crystal (LC), which can construct and flexibly manipulate arbitrary terahertz (THz) chirality. When the twist angle between the anisotropic axes of two metasurfaces θ is not 0°, the spatial mirror symmetry of the chiral metadevice is broken, resulting in a strong THz chiral response. In addition, the introduction of anisotropic LCs not only enhances the chiral response of the metadevice but also induces the flipping modulation and frequency tunability of the chirality. More importantly, by optimizing the θ, we can flexibly design the arbitrary chiral response and the operating frequency of chirality, thereby promoting the emergence of various chiral manipulation devices. The experimental results show that the maximum circular dichroism can reach −33  dB at 0.94 THz and flip to 28 dB at 0.69 THz by rotating the LC optical axis from the x to y axis, with the maximum operating frequency tunable range of ∼120  GHz. We expect this design strategy can create new possibilities for the advancement of active THz chiral devices and their applications, including chiral spectroscopy, molecular recognition, biosensing, and fingerprint detection.