Arbitrary polarization conversion for pure vortex generation with a single metasurface

TL;DR

This paper introduces a novel method to generate high-purity optical vortex beams with arbitrary polarization using a single metasurface and polarizer, simplifying previous complex setups and enabling efficient vortex creation.

Contribution

It presents a generalized theory for independent phase and amplitude control with birefringent nanopillars, allowing pure vortex generation with a single metasurface.

Findings

High vortex purity achieved with a single metasurface and polarizer

Effective control over arbitrary input polarization states

Suitable for large topological charges

Abstract

The purity of an optical vortex beam depends on the spread of its energy among different azimuthal and radial modes. The smaller is this spread, the higher is the vortex purity and the more efficient are its creation and detection. There are several methods to generate vortex beams with well-defined orbital angular momentum but only few exist allowing to select a pure radial mode. These typically consist of many optical elements with rather complex arrangements, including active cavity resonators. Here we show that it is possible to generate pure vortex beams using a single metasurface plate in combination with a polarizer. We generalize an existing theory of independent phase and amplitude control with birefringent nanopillars considering arbitrary input polarization states. The high purity, sizeable creation efficiency and impassable compactness make the presented approach a powerful complex amplitude modulation tool for pure vortex generation, even in the case of large topological charges.