Reconfigurable Dual‐Functional Switching in GST‐Based Heterogeneously Integrated THz Metasurfaces

Abstract Nonvolatile metasurfaces capable of multifunctional integration are crucial for increasing the integration density and information capacity of photonic systems. However, most existing integrated devices are volatile and require continuous external energy to maintain their functional states, which limits their further application. Here, one switchable metalens/focusing optical vortex (FOV) generator and two switchable metalenses/superposed FOV generators are designed, fabricated, and experimentally characterized. These devices achieve stable switching between two distinct optical functions through optical or thermal actuation. The first function, operating as a metalens, achieves high‐efficiency beam focusing capabilities, which are critical for applications in imaging, sensing, and compact optical systems. The second function generates FOV or superposed FOV beams, offering freedom for spatial mode multiplexing and enhanced physical‐layer security in optical communications. By heterogeneously integrating the nonvolatile phase‐change material Ge 2 Sb 2 Te 5 (GST), the silicon‐based metasurface devices exhibit stable optical response characteristics. The study of such heterogeneously integrated metasurfaces provides a new pathway for the development of high‐performance terahertz (THz) integrated photonic devices.