Programmable Wavefront Control in the Visible Spectrum Using Low‐Loss Chalcogenide Phase‐Change Metasurfaces

All‐dielectric metasurfaces provide unique solutions for advanced wavefront manipulation of light with complete control of amplitude and phase at sub‐wavelength scales. One limitation, however, for most of these devices is the lack of any post‐fabrication tunability of their response. To break this limit, a promising approach is employing phase‐change materials (PCMs), which provide fast, low energy, and non‐volatile means to endow metasurfaces with a switching mechanism. In this regard, great advancements have been done in the mid‐infrared and near‐infrared spectrum using different chalcogenides. In the visible spectral range, however, very few devices have demonstrated full phase manipulation, high efficiencies, and reversible optical modulation. In this work, a programmable all‐dielectric Huygens’ metasurface made of antimony sulfide (Sb2S3) PCM is experimentally demonstrated, a low loss and high‐index material in the visible spectral range with a large contrast (≈0.5) between its amorphous and crystalline states. ≈2π phase modulation is shown with high associated transmittance and it is used to create programmable beam‐steering devices. These novel chalcogenide PCM metasurfaces have the potential to emerge as a platform for next‐generation spatial light modulators and to impact application areas such as programmable and adaptive flat optics, light detection and ranging (LiDAR), and many more. This work establishes antimony trisulfide (Sb2S3) as a good low‐loss high‐refractive‐index dielectric phase‐change material to form all‐dielectric metasurfaces for programmable wavefront control in the visible spectrum. The metasurfaces experimentally demonstrate reversibly reconfigurable optical responses with large spectral shift and close to 2π phase modulation, along with beam steering and reconfigurable bound state in the continuum.