Strong terahertz chiral manipulation in double-layer metasurface sandwiched with ultrathin liquid crystals

Strong terahertz chiral manipulation plays a vital role in polarization imaging, chiral spectroscopy, and multichannel communications. Here, a composite structure based on the double-layer metasurface sandwiched with the ultrathin liquid crystal layer is proposed to realize a strong terahertz chiral manipulation. On account of breaking mirror symmetry in the propagation direction and the local field enhancement effect in the cavity, the composite structure possesses a strong terahertz chiral response. Moreover, this terahertz chiral response can achieve a large tuning range by changing the optical axis of the liquid crystal: the experimental co-polarization circular dichroism can achieve a large controllable range of −31dB to 30dB at 0.772 THz and a chirality control range from 11dB to −22dB at 0.759 THz. This composite device demonstrates rich characteristics for the feasible manipulation of THz chiral response, which has greatly promoted the development and practical application of THz polarization and chiral control devices.