Broadband and high-efficiency thermal switchable InSb metasurface for terahertz wave anomalous reflection and focusing effect

In this paper, a reflective metasurface composed of a dielectric substrate sandwiched with a double-split-ring (DSR) structure InSb and a metal ground plane was proposed in terahertz (THz) region, which can realize a high-efficient thermal switchability of circular-polarization (CP) conversion, anomalous reflection, and planar reflective focusing effect in a broadband manner. Simulation results demonstrated that the designed InSb metasurface structure can achieve high-efficient reflective CP conversion, with the magnitude of the reflected orthogonal CP wave being over 0.8 on average from 0.7 THz to 1.55 THz under the external higher thermal (T = 320 K, “On” state). Conversely, the magnitude of the reflected orthogonal CP wave is nearly zero under external lower thermal conditions (T = 240 K, “Off” state). Furthermore, the proposed InSb metasurface structure can achieve a high-efficient reflective CP conversion with an efficiency of about 0.7 under the “On” state, and a 2π phase full coverage by adjusting the oriented rotation angle (α) of the DSR structure InSb. As evidences of the concept, two InSb metasurfaces have been constructed to achieve the broadband switchable anomalous reflection phenomenon and reflective focusing effect based on Pancharatnam-Berry (PB) phase principle. The proposed metasurface has great potential in developing a dynamically tunable device for THz wavefront modulation applications in the future.