Diffractive arrays of gold nanoparticles near an interface: critical role of the substrate

TL;DR

This paper investigates how substrates influence the optical resonances of gold nanoparticle arrays, revealing critical parameters that affect diffractive coupling and resonance strength, with implications for photonic device design.

Contribution

It demonstrates that substrate properties significantly impact lattice resonances in plasmonic arrays, providing a simple analytical model to predict these effects.

Findings

Substrate-to-superstrate index contrast affects diffractive coupling.

Array-interface distance is critical for resonance strength.

A simple model accurately reproduces electromagnetic simulation results.

Abstract

The optical properties of periodic arrays of plasmonic nanoantennas are strongly affected by coherent multiple scattering in the plane of the array, which leads to sharp spectral resonances in both transmission and reflection when the wavelength is commensurate with the period. We demonstrate that the presence of a substrate (i.e., an asymmetric refractive-index environment) can inhibit long-range coupling between the particles and suppress lattice resonances, in agreement with recent experimental results. We find the substrate-to-superstrate index contrast and the distance between the array and the interface to be critical parameters determining the strength of diffractive coupling. Our rigorous electromagnetic simulations are well reproduced by a simple analytical model. These findings are important in the design of periodic structures and in the assessment of their optical resonances for potential use in sensing and other photonic technologies.