High-definition 3D suspended Archimedean spiral with broadband, spatially extended, and single-handed optical chirality enhancement in Vis-NIR range

TL;DR

This paper introduces a high-definition 3D plasmonic Archimedean spiral that exhibits broadband, spatially extended, and single-handed optical chirality in the Vis-NIR range, with potential applications in chiral sensing.

Contribution

It presents a novel fabrication method for deterministic 3D plasmonic spirals and demonstrates their broadband, extended chirality properties both numerically and experimentally.

Findings

Achieved spectrally broadband and spatially extended optical chirality in 3D plasmonic spirals.

Successfully fabricated high-definition 3D Archimedean spirals using combined focused ion beam and template stripping.

Confirmed the predicted optical response through experimental far-field chiroptical characterization.

Abstract

3D plasmonic structures can provide giant optical chirality (C) in the near field, enabling strong interactions with enantiomers for chiral sensing applications. However, these structures face several limitations, including narrow operational bandwidth constrained by resonance, flipping handedness of C around the resonant frequency, spatially confined distribution of C, and difficulty in trapping enantiomers. Our numerical predictions reveal that a 3D plasmonic Archimedean spiral (AS) exhibits spectrally broadband, spatially extended and single-handed near-field C in visible-to-near-infrared range. However, realizing highly deterministic 3D AS remains challenging. We develop an effective fabrication strategy that combines focused ion beam milling and template-stripping method to realize high-definition 3D AS. Furthermore, we experimentally characterize the fabricated structure's far-field chiroptical behavior to confirm the predicted optical response. Owing to its conical hole-like geometry, 3D AS can potentially function as a sieve for trapping enantiomer-functionalized nanoparticles in the hot zone with enhanced C for sensitive broadband chirotical detection.