A tunable terahertz broadband absorber based on patterned vanadium dioxide

A patterning vanadium dioxide (VO2) tunable broadband terahertz absorber is designed, which consists of a resonant layer of VO2 and a metallic reflector layer separated by a dielectric layer of Topas. VO2 is a phase-changing material that behaves as a metallic phase at high temperatures and an insulating phase at low temperatures. Different from conventional metal-dielectric-metal three-layer structure, the innovation of this paper is that the resonant layer adopts vanadium dioxide, which is a phase change material, not only does it increase the operating bandwidth but it also allows active tuning of the absorption amplitude by varying the temperature and hence the vanadium dioxide conductivity. By optimizing the width of the vanadium dioxide resonant layer square ring and the thickness of the dielectric layer, broadband absorption is achieved in the frequency range of 0.72–1.92 THz. Numerical simulation results show that VO2 with low conductivity then behaves as an insulating phase, and its peak absorption in the corresponding broadband absorption band is only 3%, so it can be used for the reflector. When VO2 has a high conductivity, its absorption is greater than 90% in the absorption bandwidth up to 1.2 THz. In addition, the proposed absorber is polarization insensitive under vertical incidence conditions because of the symmetry of the structure. The absorber can also maintain good absorption performance by changing the angle of incidence and polarization state. In the terahertz wave sector, the tunable terahertz absorber developed in this article has several potential applications, including detectors, sensors, stealth technologies, etc.