Offset focusing and holographic imaging based on a reconfigurable terahertz metasurface

A dual-channel reconfigurable metasurface based on vanadium dioxide (VO₂) and photosensitive silicon is proposed to realize offset focusing and holographic imaging. Based on the Pancharatnam-Berry (PB) phase principle, the three-bit quantization of the cross-reflection phase in the range of 360° is realized by rotating the in-plane mechanism of the unit. Based on the compensated phase formula, focusing theory, and Gerchberg-Saxton (GS) algorithm, the phase distributions of the metasurface are calculated, respectively. When phase change materials (PCMs) are both insulated, the array can achieve offset focusing in circular polarization. Broadband holographic imaging can be performed when both PCMs are in a metallic state. The metasurface's structure is simple, and its function is reconfigurable. The design has good potential for application in terahertz communication, imaging, and target detection. It provides a reference for the design of efficient, lightweight, and low-cost terahertz functional devices.