Thermally tunable metamaterial absorber based on strontium titanate in the terahertz regime

In this paper, a thermally tunable metamaterial absorber comprising a periodic array of metallic circle resonator with strontium titanate (STO) has been proposed in the terahertz regime. Due to the special active material, STO is adapted as the dielectric layer, thermally tunable is implemented in the absorber. A full-wave numerical simulation is performed and the results reveal that the peak absorption of the absorber reaches 99.9% at 2.48 THz when the temperature is set as 400K, and the central frequency can shift from 2.48 to 1.71 THz when the temperature varies from 400K to 200K. Furthermore, the electric field distribution and surface current distribution are investigated to better understand the absorption mechanism. Besides, the influence of the polarization angle and oblique incident angle to the absorber is studied and the results show that the peak absorption remains above 90% up to 60${}^{\circ }$of the incidence angles for the TE mode and 55${}^{\circ }$for the TM mode. The absorber can be scalable to the infrared and visible frequencies, and can be potentially applied to imaging, detection and tunable sensing.