Metasurface-Enhanced Momentum-Resolved Circular Dichroism Spectroscopy

Nanophotonic resonators can amplify weak molecular circular dichroism (CD) signals, but structural chirality from angle-dependent photoexcitation or collection may mask molecular chiroptical features. Here, we develop an achiral nanodisk array and angle-resolved spectral measurement approach that deconvolves molecular and substrate signals, enabling artifact-free chiroptical enhancement. Circular polarization-resolved momentum-space spectroscopy maps chiroptical response across wavelength and collection angle to simultaneously report intrinsic, molecular CD and extrinsic, nanostructure-induced signals in distinct optical channels. We design silicon nitride nanodisks which support a simulated ∼150-fold enhancement in the density of optical chirality averaged throughout the analyte-accessible region and spectrally aligned with thiocamphor's CD features. We validate the enhancement of low concentration and enantiomeric excess (ee) CD signals with the predicted spectral and angular sensitivity, down to 0.1 mM and across 1-25% ee. Our approach demonstrates momentum-resolved, metasurface-enhanced CD spectroscopy as a promising path to reliable, sensitive detection of molecular chirality and enantiomeric purity.