Inverse-Designed Superchiral Hot Spot in Dielectric Meta-Cavity for Ultra-Compact Enantioselective Detection

TL;DR

This paper introduces a novel inverse design method for dielectric metasurfaces that creates superchiral hot spots, significantly enhancing near-field optical chirality for ultra-compact enantioselective detection.

Contribution

It presents a two-step inverse design scheme for dielectric metasurfaces with record-high chiral field enhancements, advancing chiral nanophotonics and sensing technologies.

Findings

Achieved near-field optical chirality enhancement up to 10^4.

Demonstrated 102-fold optical chirality enhancement in a fabricated prototype.

Surpassed previous superchiral field generation efficiencies.

Abstract

Chiral nanophotonic structures have garnered considerable interest in recent years due to their potential to enhance the efficacy of chirality-sensitive biomolecular detection. Designing metaplatforms to enhance chiroptical signals under linearly polarized excitation is particularly appealing due to the minimal chiral background and the ease of controlling excitation polarization. Here, a novel two-step inverse design scheme for dielectric lossless metasurfaces with superchiral hot spots is proposed. The method extends the local density of field enhancements for non-chiral fields into the chiral regime and significantly surpasses previous enhancements in super-chiral field generation. It has been demonstrated that by leveraging the excitation of high quality factor modes with small mode volumes, it is theoretically possible to convert linearly polarized plane waves into a superchiral hot spot with record-high enhancement in the near-field optical chirality up to 104. A prototype is successfully implemented using advanced nanofabrication technologies. The optical characterization of the prototype demonstrates a 102-fold enhancement in optical chirality. The findings of this study unveil novel prospects for chiral spectroscopy with ultra-compact devices, underscoring the role of machine learning and physics-based inverse design in the development of cutting-edge, functional photonic structures.