Tunable Isotropic Absorber With Phase Change Material VO2

In the past decade, metamaterial absorber has been attracting great attention and making huge progress. Most of previous metamaterial absorbers are working with a narrow band. Some efforts to realize broadband absorber have been made from microwave, terahertz to optical frequencies, which often includes multiple resonators with different sizes or multilayer structure with different geometrical dimensions. The configurations of these designs are not simple, and they require some complicated fabrication procedures. Meanwhile, the position of absorption peak and working intensity are usually fixed once the structure of metamaterial absorber is fabricated. Here a new isotropic tunable absorber is presented with a simple vanadium dioxide structure in the terahertz region. By adjusting the geometrical size, simulation shows that our design under normal incidence can achieve broadband absorptance >90% with a central frequency of 1.815 THz in the frequency band of 1.08-2.55 THz. Working intensity of the proposed absorber can be tuned from 1.3% to near 100% by changing the conductivity of vanadium dioxide from 0 Ω ^-1 cm ^-1 to 2000 Ω ^-1 cm ^-1 . The obtained absorption spectrum is independent of incident polarization, and absorptance has a good performance when incident angle varies from 0° to 45°. The proposed design may be useful for promising applications in stealth technology, thermal emitter, and terahertz detection.