Broadband and efficient asymmetric wavefront manipulation via terahertz polarization-selective metasurface

Asymmetric manipulation of electromagnetic waves exhibits tremendous capabilities in the applications of encryption, ultrafast information processing, and communication. However, compact and broadband terahertz (THz) components for asymmetric applications are still scarce. Here, we demonstrate broadband, ultrathin, and efficient metasurface-based asymmetric transmission and wavefront manipulation in the THz region. The metasurface consists of tri-layer metallic structures separated by two flexible polyimide dielectrics. This ultrathin structure exhibits superior asymmetric response which can act as an efficient device with a high linear polarization conversion ratio over 0.9 ranging from 0.5 to 1.1 THz. We also develop THz asymmetric applications based on the flexible metasurface for beam deflector and orbital angular momentum generation. The THz time-domain spectroscopy system and spectral imaging system are used to characterize the broadband asymmetric properties. The experimental results confirm that the beam deflection and vortex waves can be realized over broadband under one linearly polarized incidence while blocked under its orthogonal incidence. This work may provide a promising route to achieve broadband asymmetric applications in information encryption, THz wireless communication, and spectroscopy applications.