Chiral emission from chirotopic nanostructures

Mirror asymmetry of electronic states or optical media is expected for the emission of chiral photons, which constrains the design of dichroic materials. Here we demonstrate that these symmetry restrictions can be relaxed by harnessing the local chirality of globally achiral materials, also known as chirotopicity. Unlike chirotopic sites in molecules whose optical effects are unknown, photonic nanostructures make possible the enhancement and deliberate localization of left- and right-handed chirotopic fields by linearly polarized light. We show that intense and highly elliptic light is emitted from achiral luminophores engulfed by such fields. Luminescence dissymmetry factors between 1.65 and −1.58, approaching the theoretical limit, are obtained for nanoparticles and dyes, which may be generalized to other luminophores. After being hypothesized by Mislow more than 50 years ago, these findings validate the concept of chirotopicity and enable its utilization in chiral photonics. Circularly polarized light typically requires mirror-asymmetric materials. Here, authors demonstrate that achiral nanostructures with locally chiral electromagnetic fields can produce highly elliptical circularly polarized emission from ordinary luminophores, achieving dissymmetry factors approaching the theoretical limit.