Thermally tunable vanadium-dioxide-based broadband metamaterial absorber with switchable functionality in the terahertz band

In this paper, a thermally tunable broadband metamaterial absorber, with switchable functionality in the terahertz band, consisted of periodically arranged vanadium dioxide (VO2) and a gold film separated by a layer of polyimide is reported, which is capable of switching from absorber to reflector through the phase change property of VO2. When VO2 is in the metallic state, three near-perfect absorption peaks localized at 3.48 THz, 5.09 THz and 7.05 THz are obtained, and the combination of them gives rise to a broadband absorption, more than 90% of absolute absorption bandwidth reaches 4.35 THz (3.1-7.45 THz) with a relative absorption bandwidth of 82.46%. When VO2 is in the dielectric state, it can switch from near-perfect broadband absorption to near-perfect reflection with the maximum intensity modulation of 92.4%. The broadband absorption is insensitive to polarization of incident beam due to symmetrical structure design and exhibits excellent tolerance for large oblique incidence angle. In addition, size changes of patterned VO2 array structure provides a large impact on the absorption performance of the thermally tunable device, especially the absorption bandwidth. Our proposed device is expected to have outstanding prospects in terahertz thermal imaging, communications, and temperature-controlled metasurface.