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

## TL;DR

This paper introduces a new design framework for metasurfaces that significantly enhances the detection of molecular chirality using optimized nanostructures.

## Contribution

A novel inverse design framework for creating superchiral metasurfaces with customizable chiral hotspots and enhanced chiral sensing capabilities.

## Key findings

- Freeform metasurfaces achieved an 820-fold chiral density enhancement.
- The platform enabled ultrasensitive detection of chiral analytes and quantification of chiral concentration.
- The framework is compatible with spin-based photonic materials for broader photonic applications.

## Abstract

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.