High efficiency dual-band coding reflection metasurface in terahertz bands

Here, we introduce a Terahertz (THz) dual-band coding reflective metasurface based on the Pancharatnam-Berry (PB) phase theory. The coding metasurface is consisted of a metal layer with hollow opening resonant ring on top of a double I-shaped deformation structure as the modified Polyimide (MPI) dielectric layer with a bottom reflective layer. It is capable of independent operation at two specific frequency bands of 0.33 THz and 0.51 THz. The high frequency double I-shaped deformation structure and the low frequency openwork resonant ring in the metal layer could be rotated and adjusted by PB phase theory to realize the continuous phase control from 0 to 2π. The coded cell at specific angles could construct coding arrays, achieving the modulation of wavefront. Due to the introduction of various encodings, the proposed metasurface enables to play a role as a vortex light generator at 0.33 THz, while it can act as a Radar Cross-section (RCS) reduction device to suppress the specular reflection of THz circularly polarized light at 0.51 THz. The simulated results show that the coding metasurface can work independently in low-frequency mode and high-frequency mode. In addition, the flexibility of the MPI layer indicates that the proposed metasurface has great potential for the integration of devices in the field of 6G communication and invisible coating.