Design of tunable dual-band absorber based on phase transition of VO2 in terahertz metasurface

Abstract

A VO₂ -based Terahertz metasurface is proposed, and the cell structure consists of two parts. One part is composed of VO₂ blocks connected by metal rings with different radius, and the other part is a VO₂ square ring. The conductance coupling between the metal structures can be manipulated by the metal-insulator phase transition of VO₂ to change the LSPR resonance mode. The transformation realizes active tunable dual-band absorption of the terahertz wave, and the effects of incident wave angle and polarization mode on the frequency response characteristics of the structure are investigated respectively. Subsequently, the theoretical study on the Terahertz metamaterial absorber is carried out, and the results indicate that the two absorption peaks are generated by the autonomous resonance of gold rings with different radius when the temperature is 25°C The absorption rate of the absorber can reach 98% and 92% at f THz = 4.16 and f THz = 5.75 , respectively. When the temperature exceeds the VO₂ phase transition temperature (68°C), the VO₂ block is combined with metal rings of different radius to form a current closed-loop which would cause unified resonance and coupling with the VO₂ square ring. Meanwhile, the absorption rate of the absorber can reach 90% at f THz = 5.27 and f THz = 8.5 . In addition, the influence of the external dielectric constant and structural parameters on the absorption characteristics is analyzed, and the applications of the absorber in sensing and thickness detection are explored to obtain the responding sensing detection performance. The conclusions are beneficial for the design of actively tunable Terahertz metasurface absorbers and have many potential applications in the detection field.