This passage presents a design of tunable terahertz metamaterials via transition between indirect and direct electromagnetically induced transparency (EIT) effects by changing semiconductor InSb’s properties to terahertz wave under optical and thermal stimuli. Mechanical model and its electrical circuit model are utilized in analytically calculating maximum transmission of transparency window. Simulated results show consistency with the analytical expressions. The results show that the metamaterials hold 98.4% modulation depth at 189 GHz between 300 K, σInSb =256000 S/m, and 80 K, σInSb =0.0162 S/m conditions , 1360 ps recovery time of the excited electrons in InSb under optical stimulus at 300 K mainly considering the direct EIT effect, and minimum bandwidth 1 GHz.

We present a novel design of tunable terahertz metamaterials. The design numerically shows that the amplitude transmission reaches 86.4%, the intensity modulation depth reaches 96.4%, the response time reaches 1360 ps, and the bandwidth exceeds 760 GHz. The metamaterial consists of a semiconductor layer and a metal layer separated by air. Under optical excitation condition, the electromagnetic properties of the semiconductor change from semi-insulating to metallic and then the amplitude transmission is mainly affected by Fabry-Perot interference and spoof surface plasmon polaritons (spoof SPPs). Furthermore, we analyze the relationship between the amplitude transmission peak determined by spoof SPPs and the design geometries using the mode expansion method. A tunable terahertz metamaterial, as a functional device, is a basic element in terahertz high-volume, wireless communication systems, which are of vital importance.