Abstract Conventional topological photonic crystals (PhCs) often face limitations in tunability and functional diversity, while metasurfaces—though versatile—lack inherent topological protection. The concept of embedding metasurfaces into robust topological PhCs is presented for diverse wave and chirality manipulations without compromising their topological nature, contributing to a twofold topology‐functionality advantage in flat optics. By embedding tailored metasurfaces into topological PhC originating from the bound state in the continuum (BIC), chirality control, phase‐gradient wavefront engineering, and generation of exceptional points are achieved, while simultaneously preserving the momentum‐space topological singularity of BICs. This unified platform transcends the single‐functionality paradigm of topological photonics, enabling multifunctional light manipulation in compact, free‐space devices for applications in chiral sensing, vortex generation, and singular optics.
Qin et al. (Sat,) studied this question.