Achieving precise dual-modulation of polarization and phase using a broadband terahertz single-cell metasurface

This paper proposes a reflective metasurface composed of a single unit structure, yet capable of achieving precise control of two degrees of freedom. By grooving two orthogonal slots on the copper ring, it enables the independent conversion of the two orthogonal components of the incident waves. Consequently, incident linearly-polarized waves can be rotated by an arbitrary angle. For circularly-polarized waves, the handedness will be reversed; furthermore, the phase of the reflected wave can cover the full 2π range by rotating the unit cells in a manner similar to that of the Pancharatnam-Berry (PB) phase metasurface. Rigorous theoretical analyses are provided. Numerical validation demonstrates that the cross-polarization reflectance of the metasurface exceeds 0.7 within the frequency range of 0.7044 to 2.0859 THz, corresponding to nearly 100% relative bandwidth. The modulation accuracy of the polarization angle can reach within 1 degree. The proposed metasurface may find applications in communication, imaging, sensing, and other fields.