Near-Field Topology-Optimized Superchiral Metasurfaces for Enhanced Chiral Sensing

The detection and discrimination of molecular chirality are essential for the advancement of pharmaceutical and biological applications. While nanophotonic platforms offer a route to enhance chiral light-matter interactions, existing device concepts for chiral sensing remain heuristic, resulting in limited chiral enhancement and control over chiral hotspot placement within nanostructures. Here, we introduce an inverse design framework that directly optimizes superchiral near fields in photonic nanostructures and demonstrate its powerful opportunities for enantioselective analysis. We first show that freeform achiral metasurfaces can be optimized to achieve an 820-fold chiral density enhancement with fully customizable chiral hotspot placement for direct molecular interaction. We then leverage this platform to demonstrate ultrasensitive detection of chiral analytes and quantitative readout of the chiral concentration and enantiomeric excess in chiral mixtures. Our framework offers a generic route to realizing superchiral nanophotonic platforms compatible with diverse spin-based photonic materials for valleytronics, chiral emission control, and topological photonics.