Single-Polarization-Channel Chiral Metasurfaces for Photon Emission Control

Achieving robust valley polarization in two-dimensional transition metal dichalcogenides at room temperature is hindered by rapid intervalley scattering, which limits the polarization contrast in photoluminescence (PL). Although tailored excitation schemes and chiral nanostructures have been explored to enhance circular polarization contrast, the presence of multiple symmetry-related optical channels often obscures the physical origin of the measured helicity. Here, we introduce a chiral metasurface engineered to support a single-polarization-channel property, providing a clean platform for dissecting spin-dependent light-matter interactions in MoS2. By suppressing competing polarization pathways, the system enables a direct and transparent mapping between excitation spin, structural handedness, and emitted PL polarization, offering simple physical insight beyond simply maximizing the degree of polarization (DOP). We also developed a physical picture to describe spin-dependent interactions among the optical channels. Experimental results demonstrate a substantial increase in PL polarization, achieving a DOP of ∼±30% under circular excitation at room temperature and clearly highlighting intrinsic chirality-driven modulation. This study presents a robust and scalable strategy for deterministic valley polarization control, offering valuable design insights for integrated valleytronic applications.