Vectorial Beams With Longitudinally Varying Polarizations Generated by Surface‐Wave Metasurfaces

Abstract

Generating structured electromagnetic (EM) beams in pre‐designed manners is highly desired in photonics applications, but conventional devices suffer from the issues of bulky sizes and restricted functionalities. Although metasurfaces have exhibited powerful capabilities in controlling EM waves, they usually work under propagating‐wave (PW) excitations, being unfavorable for EM integration. Here, a generic scheme is proposed to design metasurfaces that can efficiently generate far‐field (FF) vectorial beams with longitudinally varying polarizations under surface‐wave (SW) excitations. Such metasurfaces consist of two sub‐sets of Pancharatnam‐Berry (PB) meta‐atoms with specifically designed orientation angles, each sub‐set can generate a circularly polarized FF beam with a particular spin and their interference forms the target vectorial beam. After experimentally demonstrating two benchmark metadevices for generating FF beams with homogeneously distributed polarizations, a microwave metasurface is designed and fabricated and experimentally demonstrate that it can generate a Bessel beam with longitudinally varying polarization under SW excitation. These findings significantly expand the capabilities of metasurfaces in controlling EM waves, paving the way to realize many applications in on‐chip photonics, such as chip‐integrated displays, encrypted holography, and augmented reality technology.