Photonic spin-controlled generation and transformation of 3D optical polarization topologies enabled by all-dielectric metasurfaces.

Optical polarization topology is a spatially varying polarization structure, which usually exists around the polarization singularity. In three-dimensional (3D) space, optical polarization topologies mainly contain two fundamental structures, Möbius strip and twisted ribbon, depending on the parity of half-twist number. These spectacular topologies have been widely found in the existence of electric fields from multi-beam interference. Here, we propose and numerically demonstrate that, depending on the photonic spin state of light, an ultrathin all-dielectric metasurface can achieve efficient generation and transformation of two arbitrary 3D polarization topologies. The spin-controlled, tightly-focused Poincaré beams generated by the metasurface exhibit topologically stable 3D polarization topologies around the waist of the focal point. The preparation of such optical polarization topologies may have potential applications in compact complex beam engineering, optical signal multiplexing and optical fabrication of microstructures with nontrivial topology.