Reconfigurable Terahertz Surface Plasmon Wavefront Control Using GST Metasurfaces

ABSTRACT Surface plasmons (SPs) have demonstrated exceptional potential in light‐matter interactions, photonic integrated circuits, and optoelectronic devices, making them one of the key platforms for realizing on‐chip terahertz systems. However, research on how to achieve on‐demand reconfigurability remains relatively limited. Metasurfaces, particularly active metasurfaces, play a crucial role in controlling the propagation of electromagnetic waves, providing a viable solution for achieving reconfigurable control of SPs. In this work, we propose an active strategy for SP manipulation using Ge 2 Sb 2 Te 5 (GST) metasurfaces, which enables reconfiguration by jointly engineering the propagation phase and the geometric phase of the launched SPs. As a result, the GST‐controlled phase‐state switching provides a versatile route for selecting between distinct wavefront designs, enabling more flexible switching among different functionalities. Based on this strategy, three representative SP devices were realized and demonstrated to exhibit non‐volatile reconfigurability, achieving forward switching (crystallization) via annealing and backward switching (amorphization) via nanosecond laser irradiation. The simulation and experimental results are in strong agreement, demonstrating the effectiveness of our strategy for realizing terahertz on‐chip devices.