Magnetically Induced Terahertz Birefringence and Chirality Manipulation in Transverse-Magnetized Metasurface

Active manipulation of photonic spin state and optical chirality leads to some key applications, such as in multichannel communication, polarization-sensitive imaging, chiral spectroscopy, and chiral sensing. Magneto-optical materials have unique advantages in the intrinsic transmission and magnetic control of photonic chiral spin states. Here, a scheme for dynamic terahertz (THz) anisotropy and chirality manipulations in the transversely magnetized InSb and its hybrid magneto-optical metasurface structure is presented. A special transverse photonic spin state in the InSb and a transverse-longitudinal spin coupling effect in the hybrid magneto-optical metasurface are revealed by the eigenmode analysis and numerical simulations. The strong magnetic birefringence effect induced by this spin mode is demonstrated in the experiment. Moreover, the symmetry-breaking mechanism in this magneto-optical structure leads to strong intrinsic chirality and polarization conversion. The experimental results confirm the magnetically active manipulation of spin states and their asymmetric transmission in this hybrid magneto-optical metasurface, which achieve a polarization conversion rate of near 100% and an induced intrinsic chirality of over 15 dB. This work opens a new development for active THz polarization control and chiral manipulation in the magneto-optical microstructure.