Polarization spatial diversity and multiplexing MIMO surface enabled by graphene for terahertz communications.

The terahertz (THz) frequency band has abundant spectrum resources, which is suitable for constructing communication systems with ultra-high data rates and extremely low latency. Multiple input multiple output (MIMO) devices are crucial for realizing THz communication, and the synchronous transmission and noncorrelation of different channels are the keys to MIMO technology. This paper proposes a graphene-based polarization spatial diversity and multiplexing MIMO surface (PDM-MIMOS) with 2 × 2 metasurface arrays. Dual-polarized channels can be modulated synchronously by the same metasurface modulator and received by the receiver (RX) without crosstalk. Experimental results demonstrate that the modulation cut-off frequency can reach up to 30 kHz. By constructing a continuous THz wave communication system, it is demonstrated that PDM-MIMOS can achieve spatial diversity and multiplexing, thereby improving communication quality and data rate. Furthermore, we compare the signal quality of THz communication and visible light communication under villainous weather conditions. The experiment proves that the communication reliability of THz communication is 19.4 times that of visible light communication. This work offers potential for compact, dual-polarized modulators that can be applied in THz communication, detection, and imaging.