Two-dimensional terahertz beam scanning with a programmable liquid crystal metasurface

We demonstrate a programmable terahertz (THz) metasurface enabling two-dimensional (2D) beam steering. Existing THz metasurfaces based on liquid crystal (LC) often provide insufficient continuous phase coverage, which limits the phase gradients required for synthesizing flexible and precise phase patterns. Here, we propose an orthogonally addressable architecture using dual H-shaped resonators in a reflective metal-LC-metal stack. The stacked resonators hybridize to form an electric quadrupole mode that localizes the field in the LC, while the coupled bilayer and the backside reflector establish a Fabry-Pérot (FP) cavity that further increases phase difference. As a result, a 300° continuous phase tuning is achieved by voltage control. Leveraging an orthogonal coding scheme to synthesize 2D phase gradients, we experimentally realize beam scanning with 5° steps up to angular range of ±40°. This work provides a scalable route toward intelligent THz apertures for communication and sensing.