Abstract
In the last decade, metasurfaces emerged as a diversified benchmark for on-chip nanophotonic devices due to design privilege and extraordinary manipulation of electromagnetic waves. In metasurfaces for numerous applications, polarization and wavelength multiplexing at broadband wavelengths are highly desirable to boost data and security encryption. Here we proposed a birefringent planar all-dielectric spin-multiplexed metasurface in the ultraviolet (UV) regime at broadband wavelengths for optical security encryption with high non-linear efficiency. The presented metasurface features carefully engineered silicon nitride (Si3N4) (which provides transparency at almost the whole UV regime) rectangular bars. For the proof of concept, the designed metasurface was encoded for vortex beam generation with different topological charges based on the handedness of incident light. Instead of interleaved or layer stacking reported metasurfaces, the proposed single metasurface incorporates the property of simultaneous conversion of amplitude, polarization, and phase for spin-dependent vortex beam generation at broadband wavelengths in UV. For incident left circularly polarized (LCP) light, the metasurface generates the second-order vortex beam, whereas, for right circularly polarized (RCP) light illumination, it generates the fourth-order vortex beam. The proposed work can lead a new pathway toward many applications in UV nanophotonics.