Multifold Enhancement of Chiroptical Sensing with Plasmonic Diffraction Gratings

The ability to detect and differentiate chiral substances according to their left- or right-handedness plays a crucial role in pharmacology, medicine, and biochemistry. Usually, only an enantiomer with specific handedness is safe and has therapeutic action, whereas its mirror counterpart can be inefficient or even toxic. Chiroptical sensing methods based on an angle-resolved surface plasmon resonance open prospects for detecting extremely low concentrations of chiral substances in real-time operations by stimulating intense light-matter interactions. Here, we analyze the enhancement of the intrinsic chiroptical sensitivity performance of a plasmonic platform, quantified through the dependence of differential-reflection observables on the chirality parameter. This platform is realized by structuring a thin plasmonic film into a diffraction grating. We theoretically and numerically demonstrate that the chiral sensitivity of the grating in terms of differential reflection increases by about 2 orders of magnitude compared to that of an unstructured thin film due to the effect of Rayleigh's anomaly. The results obtained demonstrate the abilities of a novel platform for chiroptical sensing and introduce a concept for boosting the chiral sensitivity with resonant and diffractive plasmonic gratings.