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

摘要

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 2 & pi; phase full coverage by adjusting the oriented rotation angle (& alpha;) 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.

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