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

摘要

A novel method of generation and synthesis of azimuthally E-polarized vortexbeams is presented. Along the axis of propagation such beams have a stronglongitudinally polarized magnetic field where ideally there is no electricfield. We show how these beams can be constructed through the interference ofLaguerre-Gaussian beams carrying orbital angular momentum. As an example, wepresent a metasurface made of double-split ring slot pairs and report a goodagreement between simulated and analytical results. Both a highmagnetic-to-electric-field contrast ratio and a magnetic field enhancement areachieved. We also investigate the metasurface physical constraints to convert alinearly polarized beam into an azimuthally E- polarized beam and characterizethe performance of magnetic field enhancement and electric field suppression ofa realistic metasurface. These findings are potentially useful for noveloptical spectroscopy related to magnetic dipolar transitions and for opticalmanipulation of particles with spin and orbital angular momentum.