Circularly polarized light (CPL) exhibits an enantioselective interaction with chiral molecules, providing a pathway toward all-optical chiral resolution. High index dielectric nanoparticles have been shown to enhance this relationship, but with a spatially varying sign (or enantiospecificity) that yields a near zero spatially averaged enhancement. Using full field electromagnetic simulations, we design metasurfaces consisting of high index dielectric disks that provide large-volume, uniform-sign enhancements in both the optical density of chirality, C (the figure of merit for sensing and spectroscopy), and Kuhn’s dissymmetry factor, g (the figure of merit for separation). By varying disk radius, we achieve local enhancements in C and g up to 138-fold and 15-fold, respectively, as well as volumetric enhancements of 30-fold and 4.2-fold. The uniform-sign enhancements in C occur near the first Kerker condition, where overlapping electric and magnetic modes maximize field strength and preserve the π/2 phase lag between the electric and magnetic fields of CPL; in contrast, uniform-sign enhancements in g occur with spectrally separated modes, where fields and phase remain optimal without reduced molecular absorption. Using first-order kinetics of the molecule thiocamphor, we show how this optically enantiopure metasurface could enable 20% enantiomeric excesses with a >2000-fold increase in yield for a photoionization reaction compared to CPL alone.

The authors gratefully acknowledge the Gordon and Betty Moore Foundation for funding through a Moore Inventors Fellowship, in addition to support from the Alfred P. Sloan Foundation. M.L.S. acknowledges a National Defense Science and Engineering graduate fellowship, and M.L. acknowledges funding from an AFOSR PECASE Grant (FA9550-15-1-0006). A.G.-E. received funding from the Fellows Gipuzkoa fellowship of the Gipuzkoako Foru Aldundia through FEDER “Una Manera de hacer Europa” and by the Basque Government PI-2016-1-0041 Project and the ELKARTEK Program through MICRO4-FAB (KK-2016/00030) and μ4F (KK2017/00089) Projects.

Peer reviewed