We proposed a multifunctional terahertz metasurface based on a double L-shaped pattern and a vanadium dioxide (VO2) film separated by polyimide. When the VO2 film is an insulator, a dual-band electromagnetically induced transparency effect is obtained, and the physical mechanism is investigated based on the current distribution and “two-particle” model. When the VO2 film is a metal, a dual-band linear-to-circular polarization converter, in which the y-polarized linear wave can be effectively converted to left-handed circularly polarized (LCP) and right-handed circularly polarized simultaneously in different bands, can be achieved. By arranging the metal pattern rotating 30°, a multifunctional antenna can be obtained. When the VO2 is an insulator, the radiation of the LCP wave is divided into four beams, with two beams reflected and two beams transmitted. When the VO2 is in the metallic state, we can only get the co-polarized reflected wave with a 21° angle. Moreover, in our design, the VO2 film does not need lithography to obtain certain patterns, which improves the convenience of fabrication and experiment. Our design opens a new way for the development of multifunctional terahertz devices and has potential applications in the terahertz communication field.

This Letter presents a double-layer structure combining a cracked cross meta-surface and grating surface to realize arbitrary incident linear terahertz (THz) wave polarization conversion. The arbitrary incident linear polarization THz wave will be induced with the same resonant modes in the unit cell, which results in polarization conversion insensitive to the linear polarization angle. Moreover, the zigzag-shaped resonant surface current leads to a strong magnetic resonance between the meta-surface and gratings, which enhances the conversion efficiency. The experimental results show that a more than 70% conversion rate can be achieved under arbitrary linear polarization within a wide frequency band. Moreover, around 0.89 THz nearly perfect polarization conversion is realized.

A polarization-insensitive, square split-ring resonator (SSRR) is simulated and experimented. By investigating the influence of the asymmetrical arm width in typical SSRRs, we find that the variation of the arm width enables a blue shift of the resonance frequency for the 0° polarized wave and a red shift of the resonance frequency for the 90° polarized wave. Thus, the resonance frequency for the 0° polarized wave and the resonance frequency for the 90° polarized wave will be identical by asymmetrically adjusting the arm width of the SSRR. Two modified, split-ring resonators (MSRRs) that are insensitive to the polarization with asymmetrical arm widths are designed, fabricated, and tested. Excellent agreement between the simulations and experiments for the MSRRs demonstrates the polarization insensitivity with asymmetrical arm widths. This work opens new opportunities for the investigation of polarization-insensitive, split-ring resonator metamaterials and will broaden the applications of split-ring resonators in various terahertz devices.