Leida xuebao (Aug 2022)
Reconfigurable Mode Vortex Beam Generation Based on Transmissive Metasurfaces in the Terahertz Band
Abstract
Combining Terahertz (THz) and Orbital Angular Momentum (OAM) technologies has great potential in high-speed wireless communication. Theoretically, OAM with different modes has strict orthogonality. The communication capacity of the system will improve significantly if OAM technology is applied to the THz communication system. Thus, the manner to generate a high-quality and dynamically controllable THz-OAM beam has been of significant interest to researchers in related fields. In this study, a double-layer transmissive metasurface that uses 3D printing as the processing method with a low cost and processing difficulty is designed. Note that the height of the unit cell for constructing the metasurface is configurable. As the height changes continuously, the phase of the transmitted wave covers 0～2\begin{document}${\pi }$\end{document} within 90~110 GHz, while the transmittance of the units is always higher than 88%. At 100 GHz, which is fed by a WR-10 standard waveguide horn antenna, OAM beams with different modes are generated by changing the relative rotation angle between the double-layer metasurface. The simulation results show that the metasurface antenna designed in this study can achieve OAM beams of \begin{document}$ l=1, \mathrm{2,3} $\end{document}, and the two-dimensional amplitude and phase results correspond with the characteristics of the corresponding modes. When \begin{document}$ l=1,\mathrm{ }2,\mathrm{ }3 $\end{document}, the OAM beam’s modal purity is 85.4%, 84.9%, and 83.4%, respectively. The measurement results include the results at frequency points of 90, 100, and 110 GHz. The results show that the OAM beam has a high-quality bandwidth of 20 GHz, which indicates that the metasurface antenna designed in this study has a wide working bandwidth at a high frequency and can be applied to high-frequency OAM communication.
Keywords
