An all-dielectric metasurface for the conversion of circularly polarized light to quasi-perfect optical vortices and focusing

Abstract Perfect optical vortices (POVs), whose radii are independent of topological charge, are highly desirable for applications in optical communication and particle manipulation. However, conventional methods to realize them typically rely on bulky optical systems or suffer from low efficiency and a narrow operating bandwidth. Here, we propose an all-dielectric metasurface operating in the visible regime that converts circularly polarized light into quasi-POVs while simultaneously focusing the generated beams. The metasurface uses crescent-shaped nanopillars that function as quasi-half-wave plates to enable efficient Pancharatnam–Berry phase modulation with near-unity polarization conversion efficiency. To suppress the dependence of vortex-ring radius on topological charge, we adopt a composite phase profile that combines spiral phase plate, axicon, and lens phases. The generated vortex beams exhibit quasi-POV behavior, with the vortex-ring radius nearly invariant across a range of topological charges. We demonstrate relatively broadband performance spanning approximately 480--600~nm, with a peak focusing efficiency of \(45.0\%\) at 580~nm. This fourfold focal pattern confirms the polarization-dependent spatial routing of multiple vortex beams with prescribed topological charges within a compact planar device. The proposed metasurface design may therefore be well suited for integrated photonic systems that require relatively broadband and polarization-controlled generation and routing of OAM-carrying vortex beams.