Asymmetric Scattering of Mirror-Symmetric Radiation from Nanostructures Coupled to Chiral Films

The interaction of radiation with chiral molecular films is not macroscopically invariant under mirror reflections and, accordingly, chiro-optical effects exist which affect the spatial symmetry of the radiation profile and which almost exclusively show up in the near field due to the large mismatch between molecule size and wavelength size. Here we prove that the scattering of a mirror-symmetric pair of plane waves by a nanowire lying on a chiral nanofilm is not mirror-symmetric with an angular dissymmetry factor that can be as large as a few tenths. Due to evanescent coupling, the nanowire efficiently experiences molecular chirality which produces a spatially asymmetric near field so that the self-consistent unbalanced excitation of nanowire photonic modes with opposite angular momenta yields asymmetric far-field interference. In addition to enriching the physical understanding of mirror symmetry breaking in chiral nanophotonics, our results could suggest ultra-efficient schemes for enantiomeric discrimination which is essential in biological chemistry and pharmacology.