Multi-Mode Polarization Converter Based on Dirac Semimetals and Vanadium Dioxide Metamaterial

A switchable multi-mode polarization converter has been designed based on a dielectric metamaterial consisting of Dirac semimetals (BDs) and vanadium dioxide (VO2), which can achieve multiple polarization conversion modes by adjusting the temperature and Fermi energy level. Functional conversion from linear-to-circular polarization (LCP) to linear polarization was achieved by changing the Fermi energy level of BDs. When the Fermi energy level is 115 meV, the metamaterial behaves linear-to-circular polarization (LCP) and the numerical simulation shows that the polarization conversion exceeds 90% in the frequency range of 3.50-6.40 THz. When the Fermi energy level is 200 meV, this design acts as a linear polarization converter. Meanwhile, it also realizes the switch from ultra-broadband to dual-broadband using the phase transition characteristics of VO2. The simulation result shows that over 90% high-efficiency polarization conversion is achieved for ultra-broadband (3.18-7.44 THz, VO2 is dielectric state) and for dual-broadband (3.38-4.25 THz and 6.35-7.50 THz, VO2 is metallic state). The physical mechanisms of the two polarization modes are discussed. Moreover, the influence of incident angle in linear polarization converter has been discussed, which displays good tolerance for incident angle. At last, a simple approach was explored to improve the polarization conversion rate (PCR). The proposed metamaterial has potential applications in biological sensing, imaging, and wireless communication.