Dynamically switchable broadband-narrowband terahertz metamaterial absorber based on vanadium dioxide and multilayered structure

We propose and demonstrate a terahertz metamaterial absorber based on vanadium dioxide (VO2) and multilayered structure with dynamically switchable broadband and narrowband absorption. Its main structure is a double absorption layer composed of VO2 rings and gold pattern. Through adjusting the conductivity of VO2, the absorber can actively transform between broadband absorption of greater than 90% in the frequency range of 2.6 THz to 6.28 THz and narrowband absorption of greater than 99.9% at 7.77 THz. A particular explanation of physical absorption mechanism based on electromagnetic resonance is presented by electromagnetic field distributions and the impedance matching theory. Furthermore, the influence of the absorption layer patterns and structural parameters on the absorber performance can not be ignored. This absorber structure also has the features of polarization insensitivity and incident wide-angle admissibility. Compared with recent studies, the absorber has improved in absorption bandwidth with the simpler design in the number of layer. The proposed absorber may find some important applications in the modulation, sensing and imaging fields.