Broadband terahertz polarization converter/absorber based on the phase transition properties of vanadium dioxide in a reconfigurable metamaterial

Based on the phase transition properties of vanadium dioxide (VO2), a metamaterial structure that can be switched between broadband linear polarization converter and broadband absorber is designed in this work. The device consists of a top metal pattern layer, a dielectric layer, and a metal reflection layer. When VO2 is in the insulated state, the metamaterial structure can be used as a linear polarization converter, and the simulation results show that its linear polarization conversion rate exceeds 90% in the frequency range of 2.71–5.18 THz. Meanwhile, it should be noted that the linear polarization conversion rate is almost 100% in 2.85–4.99 THz. Alternatively, when VO2 is in the metallic state, the designed structure can be used as a broadband absorber, and the corresponding results reveal that the broadband absorption is achieved in the frequency range of 2.63–5.27 THz. In addition, the physical principle of the metamaterial is explained using the surface current distribution and impedance matching theory, and the effects of different incident angles and different polarization angles on the metamaterial properties are discussed. The proposed structure offers simple fabrication, wide frequency band operation and multifunctional applications, and can be used in the fields of detection, communication and electromagnetic stealth.