Phase-transition-driven polarization and intensity modulation in GST metasurfaces

Abstract

Metasurfaces, especially those employing phase-change materials (PCMs) like Ge₂Sb₂Te₅ (GST), have revolutionized subwavelength light manipulation, promising enhanced reconfigurability in nanophotonic devices. Despite their potential, the limited tunability in terms of states and dimensions has hindered broader applications. Here, we propose a GST-based reconfigurable metasurface capable of simultaneously modulating transmissivity, phase, and polarization. Leveraging the full states of phase transitions from amorphous to crystalline states, the metasurface can elaborately adjust the focal spot's intensity based on amplitude and phase joint regulation. Our design exploits the refractive index shifts during phase transition and phase modulation discrepancies between the two axes of composite nanorods, allowing for dynamic transitions across three polarization states, with each state's transmittance decreasing sequentially. Furthermore, we demonstrate the metasurface's ability to transition from multichannel vectorial holography to near-perfect absorption by eliminating the limitations imposed by intermediate phase states. These advancements represent a new way to multi-dimensional, multi-state tunable photonic systems, broadening the scope for novel optical devices.