摘要
We theoretically demonstrate the first photonic spin-meron tube lattice in free space using spin-angular momentum vectors. Square-block diffraction creates C4-symmetric beams with pi /2 phase steps. Nonon diffractive element dimensions. Extending the geometry driven formalism, we show that C3 geometry of triangular block yields spin-skyrmion tubes while effective moire bilayer results in spin twistronics in free space without the need of strong near-field confinement. Stratton-Chu theory and full-vectorial finitedifference time-domain calculations both support this material-agnostic geometric driven approach as a platform to explore the symmetry-driven free-space topology.