High efficiency focusing vortex generation and detection with polarization-insensitive dielectric metasurfaces.

The optical vortex beam with an orbital angular momentum, featuring a doughnut intensity distribution and a helically structured wavefront, has received extensive attention due to its applications in nanoparticle manipulation and optical communications. In this paper, we propose high-efficiency polarization-independent vortex beam generators which are capable of transforming the arbitrarily polarized plane wave into a focusing optical vortex beam and an abruptly focusing airy vortex beam. Besides, based on holographic metasurfaces, we provide a general design scheme for detecting the topological charges. With such a design strategy, multichannel topological charge resolved devices are demonstrated, which successfully implement the detection of the topological charges from -2 to 2. The metasurfaces designed with a simple and effective method in light manipulation promise photonic applications in secure communications and other related areas.