A Broadband Dual-Polarized Reflective Metasurface for THz OAM Communication

Terahertz (THz) beams with abundant spectrum resources and low beam divergence can be combined with orbital angular momentum (OAM) beams characterized by orthogonal propagation to multifold the capacity of wireless communication systems. However, in order to support the explosive growth of massive communication data traffic, THz OAM must be further enhanced with other multiplexing technologies. Therefore, it is imperative to develop new multifunctional devices. In this article, we propose a novel broadband dual-polarized reflective metasurface, which can generate two coaxially propagating OAM beams with distinct modes for each polarization. Because of the geometric symmetry, the metasurface shows the same electromagnetic response with respect to both
${x}$
- and
${y}$
-polarized waves, thus possessing the dual-polarized property. Simulated and measured results verify that the metasurface can realize the incorporation of OAM multiplexing and polarization multiplexing in a broad frequency range of 90–110 GHz. The crosstalks from other OAM modes and polarizations are lower than −16 dB and −21 dB, respectively. Based on the metasurface, a THz wireless communication system was demonstrated by multiplexing four independent OAM beams with each channel carrying a 6-Gbaud quaternary phase shift keying (QPSK) signal, so that an aggregate 48 Gbit/s data transmission with bit error rate (BER) below 3.8e-3 was achieved. This work verifies the feasibility of metasurface for multidimensional multiplexing in the THz region, meaning the metasurface may serve as a promising candidate for ultrahigh speed THz communication systems.