Robust Circularly Polarized Luminescence via Quasi-Bound States in the Continuum in Intrinsic Chiral Silicon...

We demonstrate circularly polarized photoluminescence emission, with dissymmetry factors g _PL over 0.1, from achiral organic dye molecules by leveraging quasi-bound states in the continuum (quasi-BICs) and surface lattice resonances (SLRs) in intrinsic silicon chiral metasurfaces. We find that the g _PL associated with the quasi-BIC mode remains robust against variations in the emission angle and dye thickness due to its strong lateral field confinement. In contrast, the g _PL of the SLR mode exhibits sign inversion depending on the emission energy and the dye layer thickness. The experimental results are supported by mode decomposition analysis, helicity density analysis, and the near-field spatial distribution of the electric field. These findings illustrate the relevance of the emitter's layer thickness in optimizing the emission of circularly polarized light. They also elaborate on the robustness of chiral quasi-BICs by comparing the g _PL of SLRs and quasi-BICs, offering insights into chiral light-matter interactions and advancing the design of circularly polarized light-emitting devices.