Generation of Vortex Beams with Strong Longitudinally Polarized Magnetic Field by Using a Metasurface

TL;DR

This paper introduces a metasurface-based method to generate azimuthally E-polarized vortex beams with strong longitudinal magnetic fields, useful for advanced optical applications.

Contribution

It presents a novel metasurface design that efficiently produces azimuthally E-polarized vortex beams with high magnetic-to-electric-field contrast.

Findings

Successful metasurface design with good agreement between simulation and analytical models.

High magnetic field enhancement and electric field suppression achieved.

Potential applications in magnetic dipolar spectroscopy and optical manipulation.

Abstract

A novel method of generation and synthesis of azimuthally E-polarized vortex beams is presented. Along the axis of propagation such beams have a strong longitudinally polarized magnetic field where ideally there is no electric field. We show how these beams can be constructed through the interference of Laguerre-Gaussian beams carrying orbital angular momentum. As an example, we present a metasurface made of double-split ring slot pairs and report a good agreement between simulated and analytical results. Both a high magnetic-to-electric-field contrast ratio and a magnetic field enhancement are achieved. We also investigate the metasurface physical constraints to convert a linearly polarized beam into an azimuthally E- polarized beam and characterize the performance of magnetic field enhancement and electric field suppression of a realistic metasurface. These findings are potentially useful for novel optical spectroscopy related to magnetic dipolar transitions and for optical manipulation of particles with spin and orbital angular momentum.