Numerical investigations of spin-multiplexing perfect vortex beam generator via dielectric metasurface at telecommunication wavelengths

Abstract

The ring structure radius of a perfect vortex beam (PVB) is invariant to topological charge, offering promising applications in optical communication, particle manipulation, and quantum optics. Integration of PVBs into on-chip optics remains challenging because complex and bulky optical devices are conventionally applied to generate PVBs. This paper reports that PVBs at telecommunication wavelengths can be generated through phase modulation in a single dielectric metasurface. The metasurface enables to generate PVBs with two distinct topological charges under orthogonal circular polarization illumination by employing a spin-multiplexing design strategy. Numerical simulations demonstrate that the radius of a PVB can be manipulated by modifying the structural parameters of the designed metasurface with high design flexibility. Further modulation of the polarization state of the incident light allows for the linear superposition of two PVBs with orthogonal circular polarization states to create a perfect Poincaré beam (PPB), which is characterized by a vectorial optical field on a higher-order Poincaré sphere. Our results introduce a straightforward method to develop versatile nanophotonic platforms for complex structured light generation and polarization engineering.