Enhancement of Optical Chirality Using Metasurfaces for Enantiomer-Selective Molecular Sensing

Circular dichroism (CD) is a physical property observed in chiral molecules by inducing the difference of absorption between left- and right-handed circularly polarized light (CPL). Circular dichroism spectroscopy is widely used in the field of chemistry and biology to distinguish the enantiomers, which typically show either positive or severe side effects in biological applications depending on the molecular structures' chirality. To effectively detect the chirality of molecules, diverse designs of nanostructured platforms are proposed based on optical resonances that can enhance the optical chirality and amplify the signal of circular dichroism. However, the underlying physics between the optical chirality and the resonance in a nanostructure is largely unexplored, and thus designing rules for optimal chiral detection is still elusive. Here, we carry out an in-depth analysis of chiral enhancement (C enhancement) in nanostructured surfaces to find the relationship between optical resonances and chirality. Based on the relations, we optimize the nanostructured metasurface to induce effective chiral detection of enantiomers for diverse conditions of molecule distribution. We believe that the proposed designing rules and physics pave the important pathway to enhance the optical chirality for effective circular dichroism spectroscopy.