Enhancing Scattering Circular Dichroism of Chiral Substrate via Mie Resonances

Chirality plays a pivotal role in the interaction between light and matter, yet detecting chiral signals from natural materials remains a challenge, necessitating the enhancement of their intensity. In this study, we present an approach to investigate substrate chirality through exploiting light scattering from Mie particles. To comprehensively analyze the scattering phenomenon, we theoretically derive the T-matrix for a nonchiral Mie sphere positioned on a chiral substrate. Unlike the Mie sphere in free space, our derivation accounts for the intricate coupling between the scattered light by the sphere and the reflected light by the substrate. Employing the T-matrix framework, we calculate the scattering power and circular dichroism spectra. Our findings reveal a remarkable augmentation of chiral signals originating from the substrate, thanks to the Mie resonance within high-index spheres. This research underscores the feasibility of probing local chiral properties in the vicinity of a sample surface, promising new insights into chiral interactions at the nanoscale.