A new design of a tunable broadband ultra-thin THz metamaterial absorber basing on vanadium dioxide

In this paper, we propose a new design of a tunable broadband ultra-thin terahertz (THz) metamaterial absorber (MMA). The lowest layer of the absorber is vanadium dioxide (VO2) square ring layer embedded in the intermediate dielectric layer. The tunability of the MMA can be realized by changing the temperature-dependent conductivity of VO2. A total effective absorption band of 0.9 THz and three absorption peaks at higher frequencies can be achieved, which is different from most MMAs whose absorption bands are only at lower frequencies. In transverse electric (TE) mode, the proposed MMA is insensitive to the change of angle of incident waves in a wide range, and the absorptivity increases with the angle of incident waves in transverse magnetic (TM) mode. At the same time, we illustrate the relationship between absorptivity and polarization angle and verify that the proposed MMA is insensitive to polarization angle to a certain extent. In addition, the thickness of the proposed MMA is only 6.85 μm with the most basic sandwich structure which is simpler than most of the same type of the MMAs.