Broadband tunable terahertz metamaterial absorber having near-perfect absorbance modulation capability based on a patterned vanadium dioxide circular patch

Abstract

A new tunable broadband terahertz metamaterial absorber has been designed based on patterned vanadium dioxide (VO2). The absorber consists of three simple layers, the top VO2 pattern layer, the middle media layer, and the bottom metal layer. Based on phase transition properties of VO2, the designed device has excellent absorption modulation capability, achieving the functional transition from broadband absorption to near-perfect reflection. When VO2 is in the metallic state, there are two absorption peaks observed at frequencies of 4.16 and 6.05 THz, exhibiting near-perfect absorption characteristics; the combination of these two absorption peaks gives rise to the broadband phenomenon and the absorption bandwidth, where the absorbance exceeds 90% and spans from 3.40 to 7.00 THz, with a corresponding relative absorption bandwidth of 69.23%. The impedance matching theory, near-field patterns, and surface current distributions are provided to analyze the causes of broadband absorption. Furthermore, the broadband absorption could be completely suppressed when VO2 presents the dielectric phase, and its absorbance could be dynamically adjusted from 100% to less than 0.70%, thereby achieving near-perfect reflection. Owing to its symmetrical structure, it exhibits excellent performance in different polarization directions and at large incidence angles. Our proposed absorber may have a wide range of promising applications and can be applied in a variety of fields such as communications, imaging, sensing, and security detection.