Active Switching of Orbital Angular Momentum of Light Using Metasurfaces Incorporating Vanadium Dioxide

The growing demand for orbital angular momentum (OAM) in optical communications calls for compact efficient beam-control platforms. Metasurfaces have emerged as a powerful tool for generating OAM beams, yet most designs remain static. Vanadium dioxide (VO₂), a phase-change material, with its reversible insulator-to-metal transition offers a promising path to dynamic control. However, in existing VO₂ integrated metasurfaces, its potential is underexploited. It is often used as a thin film that fails to exploit the full refractive index variance. Although recent attempts have incorporated VO₂ into nanostructures, they remain limited to binary-phase modulation or involve fabrication-complex structures that are unsuitable for applications in the telecommunication waveband. Here, we propose a reflective active metasurface at 1500 nm that integrates VO₂ into metal-insulator-metal meta-atoms. Our design strategy selects the geometry of each meta-atom based on the phase difference across VO₂ transition, and its orientation is governed by the proposed equations. Our design enables efficient OAM switching with large topological charge leaps. We numerically demonstrate three metasurfaces that switch OAM states between ℓ = (-1, -3), l = (-2, -3), and (4, -1). Our work establishes a versatile and fabrication-friendly platform for active OAM manipulation, promising advanced applications in high-capacity optical communications.