Polarization-to-Spatial Degree-of-Freedom Converter with Cascaded Metasurfaces

Nanostructured metasurfaces have enabled unconventional structuring of light fields and therefore provided new opportunities in manipulating photon states in quantum optics for individual or entangled photons. Despite the drastic upscale of degrees of freedom allowed in a metasurface design, the lack of non-locality in light field modulation caps the efficiency of multiplex light manipulation using a planar metasurface [1]. Such efficiency cap limits the efficiency of a variety of applications, such as the generation of non-local skymion of entangled photon pairs [2], which requires a complete conversion of the degree of freedom of a photon from polarization to orbital angular momentum topological charge. The efficiency of such conversion is limited to 50% with current bulk optics or metasurface approach due to the lack of non-locality [3].