Room-Temperature Circularly Polarized Single Photon Emission from Eu³⁺/Organic Complexes Coupled to Chiral Plasmonic Nanocavity

Room-temperature circularly polarized single-photon sources are crucial for quantum information and photonic technologies. Here we integrated europium (Eu 3+ )-doped organic complexes with chiral plasmonic nanocavities using helicoid-on-mirror (HoM) architecture, achieving giant circularly polarized emission with quantum yield of 40% and dissymmetry factor ( g lum ) of 0.40 ± 0.02. The HoM’s superchiral hotspot enhances chiral emission through the Purcell effect. Nonlinear dynamics confirms the transition from spontaneous to stimulated chiral photon generation with reduced threshold power. Time-resolved fluorescence spectroscopy shows enhanced radiative rates (0.7 μs vs 360 μs bulk), indicating efficient plasmon–exciton coupling. Single-photon emission with circular polarization characteristics is demonstrated by photon antibunching ( g (2) = 0.30 ± 0.05) at room temperature when the pumping power is below 20 μW. This integration of lanthanide photophysics with chiral plasmonics provides scalable pathways for room-temperature quantum chiral photonics, with applications in quantum information encoding, chiral sensing, and circularly polarized organic light-emitting diodes.