Spin-decoupled metasurfaces for the generation and manipulation of structured light

In recent years, nanophotonics has revolutionized the control of light by enabling the manipulation of amplitude, phase, and polarization at subwavelength scales. Within this framework, dielectric metasurfaces have emerged as ultracompact and versatile platforms for the generation of structured light, allowing the creation of complex optical states carrying orbital angular momentum, vectorial polarization textures, and topological singularities. This thesis investigates the design, fabrication, and optical characterization of spin-decoupled metasurfaces that combine dynamic and geometric phase control to encode independent phase profiles for opposite circular polarizations. Building on this approach, a series of innovative devices is demonstrated, including perfect vector beams, multifocal OAM-independent vortices, helico-conical beams, and optical skyrmions and bimerons with tunable or reconfigurable topology, as well as polarization-(in)sensitive metamultipliers for the manipulation of OAM beams. The research integrates finite-element simulations, meta-atom library optimization, and high-resolution electron-beam nanofabrication, together with advanced polarimetric and interferometric characterization to reconstruct amplitude, phase, and local polarization distributions. The results advance the fundamental understanding of structured light and metasurface physics and pave the way toward compact, multifunctional photonic components for classical and quantum optical technologies