All-Dielectric Terahertz Metasurfaces for Multi-Dimensional Multiplexing and Demultiplexing

Terahertz (THz) communication is an up-and-coming technology for the sixth-generation wireless network. The realization of ultra-high-speed THz communication requires the combination of multi-dimensional multiplexing schemes, including polarization division multiplexing (PDM), mode division multiplexing (MDM), and wavelength division multiplexing, to increase channel capacity. However, most existing devices for MDM in the THz regime are single-purpose and incapable of multi-dimensional modulation. Here, all-dielectric metasurfaces are designed for 2D multiplexing/demultiplexing, which takes the lead in combining orbital angular momentum (OAM) MDM and PDM in the THz regime. The multi-functional wavefront phase modulations and interleaved meta-atom arrangements are used to realize polarization-selective multichannel OAM mode (de)multiplexing, in which the linear-polarized 4-channel and circular-polarized 6-channel demultiplexing are experimentally demonstrated. Between different linear-polarized channels, the measured maximum crosstalk is -16.88 dB, and the isolation of each channel can be greater than 10 dB in a range wider than 0.1 THz. This study paves the way for multi-dimensional multiplexing in the THz regime, which may benefit extremely high-capacity and integrated THz communication systems. The proposed design strategy is readily applied to multi-functional metasurfaces for microwaves and far infrared light, facilitating the development of multiplexing technology and OAM-related applications. A straightforward strategy to realize compact 2D demultiplexing of orbital angular momentum modes and polarization states by using the versatile all-dielectric metasurfaces is demonstrated in the THz regime. The measured isolation and insertion loss indicate that this few-channel multiplexing strategy holds high promise for integrating into broadband THz communication systems. image