A liquid-crystal-based programmable metasurface for full-space terahertz beam steering

Abstract

Terahertz (THz) waves have shown unique advantages in fields such as communications and imaging, but their dynamic beam modulation is limited by single functionality and space utilization of traditional devices. Although programmable metasurface (PM) provides a new approach for dynamic control, full-space (transmission/reflection synergy) THz wave modulation devices still face challenges such as poor material adaptability and high coding complexity. In this paper, we propose a liquid crystal (LC)-based full-space PM with 1-bit coding by electrically controlling the molecular orientation of the LC to achieve 180° phase coverage in the transmission (0.26–0.34 THz) and reflection (0.65–0.70 THz) dual bands, respectively. Based on the Simulated Annealing-Gerchberg–Saxton model, the phase distribution is optimized to achieve multi-beam steering. The power efficiency of the target beam is greater than 70% with good stability and directivity. As a proof of concept, we design and fabricate LC-based PM with 20 independently controlled subarrays. We experimentally demonstrate that the proposed PM is capable of active beam steering in reflective space, and experimental measurements match simulation results. This work provides a new device basis for future THz communication and imaging systems.