Broadband and high transmission multifunctional metasurface based on-tunable InSb

Transmissive terahertz (THz) metasurfaces have potential applications in imaging, biosensing, and optical communications. Traditional THz metasurfaces have a lot of problems such as non-adjustable spectra and low transmission efficiency. In this paper, discrete transmission phase principle and temperature-tunable material indium antimonide (InSb) are used to complete full phase coverage in the frequency range from 0.75 THz to 0.95 THz. Then a series of broadband temperature-controlled transmissive functional metasurfaces, such as anomalous refractors, focusing metalens, and orbital angular momentum (OAM) beam generators, are realized. The working states of these proposed metasurfaces can be switched from "ON"to "OFF'' by adjusting the temperature of InSb from 220 K to 360 K. In addition, by adding vertical copper plates to form a Fabry-Perot (FP) cavity-like structure, the transmission efficiencies of these metasurfaces are improved drastically to 60%. This work provides a method for designing tunable high performance multifunctional metasurface, which is expected to broaden the practical application of metasurfaces in the THz band.