Steering chiral luminescence with silicon metasurfaces

Circularly polarized luminescence is crucial for applications in displays, optical communication, bio-imaging, and medical diagnostics. In this work, we investigate the intrinsic and extrinsic chiro-optical properties of silicon metasurfaces. For extrinsic chiral luminescence, we employ metasurfaces with unit cells composed of dimers of Si nanodisks with different diameters, inducing the formation of quasi-bound states in the continuum (Q-BICs). The coupling between Q-BICs and the emission of the dye molecules results in highly directional, circularly polarized luminescence with a dissymmetry factor of 1.6. For intrinsic chiral luminescence, we examine metasurfaces with unit cells formed by dimers of displaced Si nanorods of equal length. We theoretically investigate the circular dichroism with the helicity density in the near-field. Experimentally, we demonstrate intrinsic chiral luminescence with a dissymmetry factor of 0.2 in an optical mode supporting a bound state in the continuum at the Λ-point. These findings provide new insights into the manipulation of chiral luminescence with dielectric metasurfaces, improving our understanding of chiral light-matter interactions, and guiding the development of chiral light-emitting devices.