Liquid crystal-modulated reconfigurable multifunctional reflective metasurface for terahertz polarization conversion

The precise manipulation of terahertz (THz) wave polarization via metasurface (MTS) engineering is increasingly crucial for advanced photonic applications. This study introduces a multifunctional, reconfigurable polarization-conversion MTS for THz frequencies, integrating tunable liquid crystals materials with multi-resonant metallic unit cells. Numerical simulations reveal that, under a bias voltage of 20 V, the proposed MTS enables dynamic polarization reconfiguration across three distinct frequency bands: (1) conversion from cross-polarized to left-handed circular polarization (LHCP) between 0.270 and 0.279 THz, (2) conversion from cross-polarized to right-handed circular polarization (RHCP) from 0.406 to 0.417 THz, and (3) conversion from LHCP to cross-polarized from 0.423 to 0.435 THz. A prototype consisting of a 40×40 array was fabricated utilizing liquid crystal injection and photolithography techniques. Experimental measurements exhibit excellent agreement with the simulation results. The proposed design achieves comprehensive control over the polarization state of linearly polarized THz waves, enabling conversion into cross-polarized, LHCP, or RHCP states. This approach offers exceptional versatility in multiband polarization manipulation, holding great potential for THz communication, sensing, and imaging applications.