Optical radiation manipulation via topological polarization singularities

Bound states in the continuum (BICs) and unidirectional guided resonances (UGRs) can be controlled by manipulation of the topological polarization singularity (TPS). Previous studies have shown that the BICs can be generated by the vortex polarization singularities (V points) with the same topological charge in upward and downward radiation. Here, we propose a class of off-Γ hetero-topological charge BICs constructed from a pair of V points with opposite topological charges under a structure with inversion symmetry. In addition, a pair of circular polarization states (C points) in the upward or downward radiation can incompletely block radiation to form quasi-UGRs. This implies that radiation can be controlled by manipulating TPSs. Our findings provide new, to the best of our knowledge, insights into the generation of off-Γ hetero-topological charge BICs and the important role of manipulating topological polarization singularities in the light-matter interaction.