Tunable Plasmonic-GeTe Metasurfaces—From Supercell Plasmonic Mode to QBIC

Metasurfaces, engineered photonic structures composed of subwavelength scatterers/emitters (meta-atoms), have revolutionized the precise and dynamic control of thermal radiation, enabling narrowband, directional, and polarized emission properties. A tunability mechanism can then be incorporated to facilitate real-time dynamics, holding significant promise for applications in thermal infrared lighting, sensing, imaging, and energy harvesting. Chalcogenide phase-change materials offer important advantages for achieving post-fabrication tunability in metasurfaces due to their drastic optical contrast, fast switching speed, and long-term stability. In this work, we developed a supercell plasmonic-Germanium Telluride (GeTe) metasurface facilitating versatile dynamics. Rather than using a continuous layer of GeTe, we discretized and incorporated GeTe with gold as meta-atoms. Through supercell design, we can realize a plasmonic mode for ultra-broadband and quasi-bound states in the continuum (QBIC) for ultra-narrowband tunability. Our approach represents a significant advancement in chalcogenide-based active metasurfaces for thermal and infrared photonics.