Intrinsically Chiral 1D Planar Photonic Crystal Slabs

Abstract Controlling intrinsic chiral light‐matter interactions are important for various fields. This usually relies on structures with mirror‐asymmetric 2 or 3D geometries, while their discovery in 1D planar nanostructures remains elusive. Here, the material anisotropy is resorted to break the mirror symmetry of 1D planar photonic crystal slabs, which exhibit intrinsic chiroptical responses despite their geometric non‐chirality. Two distinct types of anisotropy‐assisted at‐Γ circular polarization states are unveiled in 1D planar photonic crystal slabs. Specifically, the first type of at‐Γ circular polarization states exhibits identical chirality and topological charges () of on two sides of 1D photonic crystal slabs with planar chirality, while the second type of at‐Γ circular polarization points, arising from the bulk Fermi arc, has opposite chirality and an identical on two sides of 1D photonic crystal slabs with intrinsic 3D chirality. Furthermore, the intrinsic chirality induced by material anisotropy is predictable and chirality switching does not require changes to the geometry, facilitating the realization of ideal chiral bound states and spin‐momentum‐locked radiation. This work opens new ways to realize the maximized optical chirality in the applications of quantum science, thermal radiation, medicine, lasing, and others.