Reconfigurable Terahertz Surface Plasmon Focusing Using Nonvolatile Phase‐Change Metasurfaces Based on Electromagnetically‐Induced‐Transparency Coupling

ABSTRACT Surface plasmons (SPs) are pivotal for wave manipulation in terahertz on‐chip systems, owing to their remarkable subwavelength confinement capabilities. Nonetheless, existing techniques for coupling SPs often struggle to achieve versatile broadband propagation and dynamic multi‐frequency control. In this study, we introduce a nonvolatile and reconfigurable terahertz surface plasmon (SP) focusing device that integrates phase‐change material Ge 2 Sb 2 Te 5 (GST) into metasurfaces with electromagnetically‐induced‐transparency (EIT) coupling. The dynamic modulation of the SPs focus is enabled by the reversible phase transition of GST between its amorphous and crystalline states. This modulation is accomplished through precise manipulation of resonance loss in meta‐atoms during thermal annealing and laser irradiation. Experimental results, corroborated by simulations, reveal a high modulation depth (more than 70%) and efficient modulation of SPs focus between points F 1 and F 2 under x ‐polarized light. Additionally, a dual‐frequency design that broadens the operational frequency channels is further demonstrated, allowing for flexible SPs focus modulation at 0.6 and 0.75 THz. This groundbreaking methodology lays the foundation for future adaptive, on‐chip SPs devices in telecommunications and sensing applications.