LAUSR

Topological defects are nonsmooth field configurations with singularities that widely exist in physics and multidisciplinary areas. Here, we introduce near-field polarization evolution and the resulting topological spin states in a system of silicon-based coupled waveguides. The topological spin structures originate from 3D evanescent field coupling that transforms the trivial transverse spin into the topological spin states in a 2D plane. Moreover, we show that the periodic coupling of higher-order electromagnetic modes can produce intriguing spin defect (singularity) arrays, including those with alternately topological charges of ±1. These findings may further expand the family of electromagnetic topological structures, and open new avenues to engineer photon emission and light-matter interactions on integrated photonic platforms.