Tunable ultra-broadband terahertz metamaterial absorber enabled by high-order resonances of single square VO₂ patch

In this paper, a tunable ultra-broadband terahertz (THz) metamaterial absorber (MA) enabled by high-order resonances of single square VO₂ patch is proposed and theoretically investigated. Despite the simple resonant structure, the absorptance of designed MA goes beyond 90% in the frequency range of 1.07–4.92 THz and the relative absorption bandwidth is 128.54%. In addition, we can adjust the absorptance of proposed MA from 20 to over 90% by changing the conductivity of VO₂. Our designed MA exhibits the polarization independence and wide incident angle stability. The ultra-broadband absorption of proposed MA is supported by the fundamental and high-order resonant modes of single square VO₂ patch, which is totally different from other tunable broadband MAs that only utilize the fundamental resonant modes of different VO₂ patterns.