Thermally switchable polarization-insensitive metasurface toward adaptive control of transmission and absorption in the terahertz regime

This paper presents a polarization-insensitive, low-profile multifunctional metasurface (MS) structure in the lower terahertz (THz) regime suitable for sensing, biomedical, and 6G communication applications featuring a unique combination of passive elements. The multi-functionality arises owing to the incorporation of a thermally switchable vanadium dioxide (VO 2 ) layer, which enables the structure to operate either as a dual-band transmissive or dual-band absorptive MS. The implemented structure features a single meta-layer to achieve better compatibility and integration with supporting devices and infrastructures. The structure offers dual transmission bands with bandwidths of 0.125 THz and 0.057 THz for temperatures below 340 K, while above 340 K, the structure performs as a dual-band absorber with absorption bandwidths of 0.0194 and 0.0419 THz, respectively. The structure maintains angular stability up to 60° for both polarizations of the incident electromagnetic wave apart from the polarization insensitivity due to inherent four-fold symmetry of the unit cell of the MS. The numerical analysis has been validated with an in-house equivalent circuit model developed step by step. Being compact in nature, the proposed MS is suitable for applications toward biomedical sensing, next-generation 6G communication systems, and beyond.