Generation of multichannel-focused vectorial-structured light along the optical path with a Fresnel zone metasurface

The manipulation of focused vector beams (VBs) with metasurfaces is an important topic and has potential applications in classical and quantum fields. However, the generation of the multichannel-focused VBs along the optical path is more challenging. In this study, we propose a Fresnel zone (FZ) metasurface comprising two sets of metallic nanoslits to generate focused higher-order Poincaré (HOP) and scalar beams in the cross- and co-polarization channels along the optical path. The same helical and the opposite radial gradient phases are constructed on two interleaving sets alternately arranged on FZs. A spin-independent propagation phase as an additional degree of freedom is introduced to break the conjugated symmetry of the Pancharatnam-Berry phase, thus realizing the arbitrary manipulation of the polarization states of HOP beams generated in two cross-polarization channels. The theoretical analysis, simulations, and experimental results all demonstrate the feasibility of the designed method for the longitudinal manipulation of complicated vector light fields. This study extends the manipulation of multichannel VBs from two-dimensional to three-dimensional space and is significant for miniaturized and spatially multiplexed devices in various conventional and quantum applications.