Synergistic Control of Multi‐Type Polarization Singularities in a Lieb Photonic Crystal Slab

ABSTRACT Polarization singularities provide exceptional control over light, yet their potential is limited by challenges in ‌controllably‌ steering individual singularities and coordinating them collectively in the momentum space. We address this challenge by mapping the evolutionary pathways of multi‐type singularities from bound states in the continuums (BICs) to degeneracy‐associated polarization singularity in a dielectric Lieb‐lattice photonic crystal slab. We demonstrate that a single parameter can orchestrate the birth, motion, and interconversion of singularities across different classes and bands. This capability enables three fundamental control modalities: (1) deterministic topological charge switching of Γ‐BICs through bifurcation; (2) continuous trajectory control of off‐Γ BICs along symmetry directions; (3) precise positioning of Dirac‐type degeneracy‐bound singularities. Significantly, our approach overcomes the traditional confinement of Dirac‐type degeneracy‐linked polarization singularities to high‐symmetry locations, enabling their free migration throughout the momentum space. Our findings establish a new paradigm for synergistic singularity manipulation in planar photonics, and the underlying mechanism can be applied to other wave systems.