Tunable broadband absorption and broadband linear polarization converter based on vanadium dioxide

Abstract A composite dielectric metamaterial based on vanadium dioxide (VO 2 ) is proposed to achieve flexible switching between two functions, broadband absorption, and polarization conversion, by adjusting the VO 2 conductivity. The designed metamaterial functions as a broadband absorber when VO 2 is in the metal phase. The absorber consists of a VO 2 top structure, a silicon dioxide (SiO 2 ) dielectric layer, and a VO 2 thin film. Numerical simulation ns show that the absorber can absorb up to more than 90% in the frequency range of 3.22 ∼ 8.51 THz, and due to the symmetry of the structure, the absorber is characterized by polarization-insensitive properties and good absorption over a wider incidence angle. When VO 2 is in the insulator phase, the designed metamaterial has a cross-polarization conversion function. The linear polarization converter primarily comprises an I-beam metal, a SiO 2 dielectric layer, and a gold substrate layer. Numerical simulations demonstrate that the linear polarization converter accomplishes a line polarization conversion rate (PCR) greater than 90% within the 1.40 ∼ 4.11 THz frequency range, attains a close to 100% cross-polarization conversion rate (PCR) at 1.46, 1.95, 3.0, and 3.97 THz. To confirm the wave absorption mechanism of the absorber, we utilize the impedance matching theory to analyze it. The proposed switchable bifunctional metamaterials present significant potential for broader applications in future terahertz communication, imaging, stealth technology, and related fields.