Design of multifunctional metasurface devices with tunable propagation properties.

The integration of terahertz (THz) technology with metasurfaces has attracted attention as it enables the fabrication of compact, high-performance, and tunable photonic devices. However, extensive investigation of metasurfaces was limited to a narrow THz range or manipulating a single mode of electromagnetic waves, absorption, reflection, or transmission, without achieving multi-band or broadband switching. This capability constrains metasurface adaptability in modern and reconfigurable systems. To tackle this issue, this study proposes a thermally tunable multifunctional metasurface device (MMD) with switchable propagation of absorption, reflection, and transmission across 0.1-10 THz. The design consists of phase change materials vanadium dixoide (VO) and GeSbTe (GST) to provide instantaneous control of transmission and reflection. A polytetrafluoroethylene (PTFE) dielectric spacer used for impedance matching and a graphene structure designed to introduce multi-band absorption. The finite-difference time-domain (FDTD) modelling outcomes reveal that the proposed MMD exhibits two transmission peaks with an average efficiency of 92.03%, two distinct absorption peaks with an average efficiency of 95.08%, and strong reflection was recorded with an average efficiency of 90.99%. This level of precision supports the applicability of the design in systems where control of frequency, with smooth switches, is required. The proposed switchable metasurface structure may hold significant potential and can be used as radomes for radars, wireless communication systems, switches, and stealth.