Full-Space Wavefront Shaping of Broadband Vortex Beam with Switchable Terahertz Metasurface Based on Vanadium Dioxide

Abstract

Currently, vortex beams are extensively utilized in the information transmission and storage of communication systems due to their additional degree of freedom. However, traditional terahertz metasurfaces only focus on the generation of narrowband vortex beams in reflection or transmission mode, which is unbeneficial for practical applications. Here, we propose and design terahertz metasurface unit cells composed of anisotropic Z-shaped metal structures, two dielectric layers, and a VO2 film layer. By utilizing the Pancharatnam–Berry phase theory, independent control of a full 2π phase over a wide frequency range can be achieved by rotating the unit cell. Moreover, the full-space mode (transmission and reflection) can also be implemented by utilizing the phase transition of VO2 film. Based on the convolution operation, three different terahertz metasurfaces are created to generate vortex beams with different wavefronts in full-space, such as deflected vortex beams, focused vortex beams, and non-diffraction vortex beams. Additionally, the divergences of these vortex beams are also analyzed. Therefore, our designed metasurfaces are capable of efficiently shaping the wavefronts of broadband vortex beams in full-space, making them promising applications for long-distance transmission, high integration, and large capacity in 6G terahertz communications.

Actively Tunable “Single Peak/Broadband” Absorbent, Highly Sensitive Terahertz Smart Device Based on VO2

“…The conductivity σ will vary with the phase change of the vanadium dioxide film. From the relationship between the dielectric constant and the conductivity of the material, we are able to obtain the relational equation for the conductivity of vanadium dioxide films at various temperatures in the phase transition process, as shown in Equation (3) [35,36].…”

Switchable dual-functional optical vortex manipulation via cylindrical phase-change metagratings

“…As an excellent phase-change material, VO 2 possesses significant advantages in terms of versatility, ease of control, and stable performance [15], and these qualities make it an ideal material for multifunctional composite field manipulation. Moreover, as these phase-change characteristics, some works related to VO 2 have been proposed [14][15][16][17]. These designs have realized the initial exploration of tunable dual-functional devices with good performances, such as extraordinary terahertz transmission [18], which can be applied to reconfigurable filters or modulators in the terahertz frequencies.…”