Due to potential applications in next generation high-capacity wireless communication systems, generating and controlling vortex beams carrying orbital angular momentum (OAM) has received considerable attention. In this work, a scheme is proposed to generate two/four splitting vortex beams and focusing vortex beams with different topological charges under left circularly polarized and right circularly polarized terahertz waves under incidence. The meta-unit cell consists of a two-flying-fish-shaped patterned metallic top layer and an identical metallic patterned bottom layer separated by a silica layer. Full-wave simulation results agree well with that of calculation predictions. The proposed terahertz metasurface-based devices are able to carry different OAM modes and can abruptly manipulate during propagation, which indicates that such metasurface-based devices may have promising applications in terahertz wireless communication links in the future.
Most existing metasurface usually has limited channel behavior, which seriously restricts its development and application. In this paper, we proposed a multi-channel terahertz focused beam generator based on shared-aperture metasurface, which consists of a top square metal strip, a middle layer of silica and a metal bottom plate. By changing the position and size of the shared-aperture array, the designed metasurface can generate arbitrary number multi-channel focusing beams at different predicted positions. In addition, the energy intensity of focusing beams can be controlled. The full-wave simulation results show that the metasurface achieve four-channel vortex focused beam generation with different topological charges, and five-, six-, eight-channel focused beam generation with different energy intensities at frequency of 1 THz, which are in good agreement with the theoretically calculated predictions. This work can provide a new idea for the design of terahertz multichannel devices.
Due to the limitations of frequency bands and control methods, it is difficult to achieve multi-functional integration and real-time regulation of full-space metasurfaces. In this paper, we proposed a switchable transmissive-reflective mode terahertz metasurface independently depending on the incident wave frequencies and polarizations. The unit cell consists of four metallic layers, which are separated by three silicon dioxide layers. When the x-polarized wave is incident along the ± z-axis, the meta-device achieves focusing function at 1.62 THz. When the y-polarized wave is incident along the ± z-axis, the structure generates the reflective two and four splitting beams at a frequency of 0.82 THz and realizes a focused beam with a topological charge of l=±1 at a frequency of 1.65 THz. The full wave simulation results are in good agreement with the theoretical calculation predictions. The metasurface provides a new idea for the control of terahertz devices, and has a broad application prospect in the field of terahertz systems.
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