Fixed-Wavelength Cross-Modal Wavefront Reconfiguration via Phase-State Control in Sb ₂ S ₃ Metasurfaces

Reconfigurable metasurfaces offer a promising route toward compact optical systems, yet many dynamic schemes rely on spectral tuning to realize reconfiguration, which limits programmable task-level switching at a fixed operating wavelength. Here we demonstrate a nonvolatile, switchable wavefront module operating at a fixed wavelength (λ = 780 nm) using an Sb 2 S 3 phase-change metasurface. The optical transfer function is deterministically rewritten through the material phase transition, enabling two distinct processing operators within the same aperture via phase-state-controlled polarization-basis switching. In the amorphous state, the device operates in the circular-polarization basis as a beam-control module, providing RCP-addressed on-axis focusing at z = 51 μm (fwhm = 2.26 μm) and LCP-addressed off-axis beam steering with a deflection angle of 25.7°. After crystallization, it operates in the linear-polarization basis as a holographic reconstructor, enabling independent image reconstruction under x- and y-polarized illumination. Clear phase-state- and polarization-addressed channel selectivity is observed, and nonvolatile write–erase operation is demonstrated over 10 cycles while preserving the designed outputs across all four channels. This compact module supports holographic display and optical security in one state and beam pointing, scanning, and coupling enhancement in the other, providing a practical platform for integrated reconfigurable optics with deterministic on-demand function switching.