Full-space and Multi-Polarization Holograms Realized by a Non-Hermitian Bilayer Metasurface.

Multilayer metasurfaces break the mirror symmetry along the path of light propagation, thereby increasing the potential for light manipulation. Herein, a paradigm is proposed that building a non-Hermitian bilayer metasurface, which is composed of two identical, orthogonally oriented, chiral J-shaped Au structures in each layer, allows exceptional points (EPs) to exist in full-space. Specifically, in the reflected half-space that adheres to mirror symmetry, the circularly polarized eigenstates coalesce at the EP, while in the transmission half-space, where mirror symmetry is broken, the linearly polarized eigenstates converge at the EP. By considering the intrinsic property of topologically protected 2π-phase accumulation encircling both EPs, we investigated full-space holography through using circularly polarized light (in reflection half-space) and linearly polarized light (in transmission half-space).