Engineering Visible-Light Chiral Plasmonic Nanoarrays for Strong Light-Matter Interactions in Photonic Microcavities

Chiral metamaterials like plasmonic nanoarrays are attractive platforms for enhancing symmetry-breaking interactions of light with molecules and nanomaterials, providing strong chiro-optical responses due to mode confinement, design flexibility, and planar compatibility. Strong chiral responses at compatible wavelengths are essential for integrating these metamaterials with photonic systems. In the visible spectrum relevant to many chiral molecules and nanomaterials, high circular dichroism (CD) has been achieved using planar intrinsically chiral dielectric nanostructures [1]. However, these structures are thick and challenging to integrate. Recently, significant CD has been observed in two-dimensional chiral cross-slit plasmonic arrays in the infrared spectrum [2], but extending these effects into the visible range remains a challenge. Here, we address this by engineering a chiral gold cross-slit nanoarray optimized for the visible spectrum, adjusting the pattern to achieve significant chiral asymmetry. Unlike previous dielectric structures, this two-dimensional nanoarray can be embedded in planar microcavities, combining high CD, low mode volume, and a reasonable Q-factor to facilitate strong chiral light-matter interactions. By overcoming fabrication challenges associated with high-aspect-ratio gold nanoarrays and integrating into an optical cavity [3], this work advances the engineering of strong chiral interactions between light and nanomaterials.