High‐Q Topological Polarization Singularities in a High‐Dimensional Synthetic Parameter Space

ABSTRACT Engineering high‐Q topological polarization singularities within a high‐dimensional synthetic parameter space provides a route to controlling multiple degrees of freedom of light. However, achieving robust and independent tuning of multiple optical parameters simultaneously has remained a significant challenge. In this work, we overcome this limitation by constructing a 4D synthetic space that combines 2D momentum coordinates with a 2D displacement parameter space described by the displacement magnitude d and azimuthal angle θ . By applying a controllable in‐plane displacement to the central cylinder of a metasurface, we reveal a high‐Q topological polarization singularity in the displacement parameter space. This singularity is characterized by a polarization vortex with a topological charge of +1 and an inverse‐square dependence of the Q factor on the displacement magnitude. The corresponding finite‐displacement quasi‐guided resonance exhibits a nearly uniform Q factor and a linear far‐field polarization locked to θ over the investigated momentum range. A key innovation is the intrinsic decoupling of control enabled by this vectorial displacement: the Q factor and linear polarization orientation are independently tuned by d and θ , respectively. This principle, validated experimentally, establishes a robust platform for advanced light manipulation.