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Structural Optimization and Performance Analysis of a Tunable Ultra‐Broadband Terahertz Absorber

Herein, an isotropic dynamic and actively tunable ultra‐wideband metamaterial ideal absorber with simple vanadium dioxide (VO2) structure is proposed and numerically simulated in the terahertz region. The absorber consists of two coplanar resonant rings based on VO2 and a metal base layer separated by a dielectric spacer. The simulation results show that the designed absorber can achieve an excellent absorption rate of more than 90% and an absorption bandwidth of 3.50 THz in the frequency band from 2.47 THz to 5.97 THz by optimizing the geometry. By changing the conductivity of VO2 from 0 to 2000 Ω−1 cm−1, the absorption peak of the absorber can be continuously and dynamically tuned from 3.90% to 99.75%. Its absorption performance is much better than that of previously reported VO2‐based absorbers. The geometric structure is optimized by wave interference cancellation theory and impedance ‐matching theory, so as to achieve better absorption bandwidth and efficiency. The electric field distribution and the energy loss density are further discussed to explore the mechanism of the absorber. In addition, the terahertz absorber has wide‐angle absorption effect for both transverse electric (TE) and transverse magnetic (TM) waves, and the absorption spectrum is independent of incident polarization.