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

## TL;DR

This paper introduces a new metasurface design using vanadium dioxide to dynamically switch orbital angular momentum of light for optical communications.

## Contribution

A novel metasurface design using vanadium dioxide's phase transition for efficient and large-step OAM switching at telecommunication wavelengths.

## Key findings

- The metasurface enables OAM switching with large topological charge leaps at 1500 nm.
- Three metasurface designs demonstrate switching between different OAM states like ℓ = (−1, −3) and (4, −1).
- The design is fabrication-friendly and suitable for telecommunication applications.

## Abstract

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.

This work presents a novel design strategy for active metasurfaces that actively switches OAM modes. The metasurface integrates VO2 within MIM meta‐atoms. Operating at 1500 nm, the designed platform enables large leaps in topological charge. For instance, the reflected beam can be switched from a topological charge of −1 in the insulating (M1) phase to −3 in metallic (R) phase.