Photonic anti-skyrmion generation enabled by symmetry-broken spin–orbit coupling

We report the demonstration of photonic spin anti-skyrmions in nonparaxial free-space beams, filling a missing region in the topological phase diagram of photonic skyrmions. The proposed mechanism is based on spin–orbit coupling of light in a symmetry-broken system, where, in addition to the intrinsic coupling between electric and magnetic Hertz potentials, controlled perturbations are introduced to an optical vortex. These perturbations modify the in-plane rotation of spin vectors, leading to the formation of anti-skyrmionic textures. The anti-skyrmions are realized through the tight focusing of hybrid-polarized vortex beams with tailored amplitude modulation, which exhibit robust stability during free-space propagation, preserving their topological features over an extended longitudinal range. We show that the angular gap width governs the characteristic size and anisotropy of the anti-skyrmion, with the scale comparable to that of its magnetic counterparts, while the number of generated textures is constrained by the topological charge of the incident beam. This work provides a deterministic and physically intuitive route for engineering complex skyrmionic and anti-skyrmionic spin landscapes using structured light, offering opportunities for programmable topological photonics with potential applications in super-resolution imaging, nanoparticle manipulation, and optical information processing.