Tailoring the terahertz far-field radiation pattern based on asymmetric transmission of linearly polarized waves in metasurface tiles

Asymmetric transmission (AT) of linearly polarized electromagnetic (e-m) waves is a well-known phenomenon in metamaterial (MTM) structures, where transverse electric (TE) to transverse magnetic (TM) polarization conversion (and vice versa) is not the same for forward (FW)/backward (BW) excitations. In this work, we explore the linear AT phenomenon of a metasurface (MS) for controlling terahertz (THz) far-field radiation patterns. An MS formed by a bi-layered metal design exhibits strong linear AT with the magnitude of 0.5 in the frequency range of 4.4 THz to 5.1 THz, and a maximum AT of 0.67 is observed at 4.953 THz. Through full-wave e-m simulations and surface current analysis, the mechanism for the observed linear AT is validated for the proposed MS structure. Based on the linear AT, three different MS tiles are constructed for controlling THz far-field radiation patterns. It is found that the proposed tiles significantly alter the electric field pattern, 3 dB angular bandwidth, and sidelobe levels of THz far-fields for FW/BW excitations. We indicate that simultaneous controlling of the amplitude and polarization of far-field radiation patterns is essential for THz imaging, communication, and spectroscopic applications.