Surface Lattice Resonances in 3D Chiral Metacrystals for Plasmonic Sensing

TL;DR

This paper demonstrates the emergence of chiral surface lattice resonances in 3D nanohelix arrays, revealing their potential for highly sensitive circular dichroism-based biosensing by tuning plasmonic-photonic interactions.

Contribution

It introduces engineered 3D chiral nanohelix arrays exhibiting surface lattice resonances with tunable plasmonic and photonic components for advanced sensing applications.

Findings

Identification of a coupling regime with enhanced circular dichroism

Maximized refractive index discrimination through mode tuning

Foundation for high-performance chiral plasmonic biosensors

Abstract

Chiral lattice modes are hybrid states arising from chiral plasmonic particles assembled in ordered arrays with opportune periodicity. These resonances exhibit dependence on excitation handedness, and their observation in plasmonic lattices is strictly related to the chiroptical features of the fundamental plasmonic unit. Here, we show the emergence of chiral surface lattice resonances in properly engineered arrays of nanohelices, fully 3D chiral nano-objects fabricated by focused ion beam processing. By tuning the relative weight of plasmonic and photonic components in the hybrid mode, we analyze the physical mechanism of strong diffractive coupling leading to the emergence of the lattice modes, opening the way to the engineering of chiral plasmonic systems for sensing applications. In particular, we identify a coupling regime where the combination of a large intrinsic circular dichroism of the plasmonic resonance with a well-defined balance between the photonic quality factor and the plasmonic field enhancement maximizes the capability of the system to discriminate refractive index changes in the surrounding medium. Our results lay the foundation for exploiting circular dichroism in plasmonic lattices for high performance biosensing.