Phase-Change Sb₂S₃ Multilayer Fabry-Perot Devices: A Novel Approach to Nonvolatile Reprogrammable Multiphase Spatial Modulation

Nonvolatile reconfiguration of optical device characteristics at the micro- and nanoscale is essential for advancing intelligent photonics. In this study, a novel approach to nonvolatile, reprogrammable multiphase modulation is presented using multilayer thin-film Fabry-Perot devices that incorporate phase-change Sb₂S₃, facilitating low-cost customization for diverse applications. These devices are fabricated through thin film deposition and feature a pixelated multilevel phase modulation configuration via intermediate phase states of Sb₂S₃ controlled by laser direct writing. The multilayer structures employ a stratification strategy to control grain size and minimize domain formation in the crystalline Sb₂S₃ films, effectively mitigating refractive index inhomogeneity caused by birefringence. The experiments achieved multilevel phase modulations with a maximum reflectance phase modulation exceeding 1.6π. The resulting multiphase holograms effectively eliminate the twin image effect often encountered in binary-phase holograms, demonstrating the capability of the devices for holographic image reconstruction. Leveraging the unique properties of phase-change Sb₂S₃, the proposed method of etching-free, pixelated laser-writing fabrication provides a versatile platform for developing reprogrammable diffractive optical elements suitable for a wide range of intelligent photonics applications.