Ultra-broadband terahertz metamaterial absorber based on a hollow vanadium dioxide circular-truncated cone resonator

Terahertz (THz) broadband metamaterial absorbers with high absorptivity have been of great interest due to their potential applications. However, their limited bandwidth severely hinders their further development and wide applications. To address this issue and achieve ultra-broadband and strong absorption properties at THz frequencies, we present an ultra-broadband THz perfect metamaterial absorber using a hollow vanadium dioxide (VO2) circular-truncated cone array and a VO2 film supported by an Au ground plane. Simulated results show that the absorptivity of the absorber reaches more than 90% in the frequency range of 0.31-10 THz at normal incidence with a relative absorption bandwidth of 188%. At the same time, the average absorptivity in the frequency range reaches 99.2%. The physical origin of broadband perfect absorption has been elucidated by impedance matching theory and wave interference theory, respectively. The electric field distribution is further discussed to explore the physical mechanism of this absorber. Additionally, it also has the characteristics of polarization insensitivity and wide incidence angle stability. The proposed absorber can have many promising applications in the THz region, such as thermal imaging, thermal detection, and cloaking.