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

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 environment͒ can inhibit long-range coupling between the particles and suppress lattice resonances, in agreement with recent experimental results. We find the substrate-tosuperstrate 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.

Modified emission of extended light emitting layers by selective coupling to collective lattice resonances

“…These lattice resonances originate from the radiative coupling between LSPRs, enhanced by diffracted orders in the plane of the array or by refractive index guided modes in the proximity of the array. In the former case the collective resonances are known as surface lattice resonances (SLRs) [2,[4][5][6][7][8][9], while the latter are known as waveguide-plasmon polaritons [10,11] or quasiguided modes [12], depending on the degree of coupling between the localized resonances and the waveguide modes. In contrast to LSPRs, collective resonances are characterized as being weakly confined to the nanoparticles, i.e., having a large extension into the surrounding media [7,13].…”

Plasmonic surface lattice resonances on arrays of different lattice symmetry

“…The beam spot on the sample was reduced to a diameter of 30 µm by inserting a pinhole aperture between the light source and the condenser, thereby giving a beam divergence of less than 1 deg. The arrays were then index matched with oil (n = 1.515) [31,32] and the transmitted light collected with an oil immersion lens (NA of 1.25). A long-pass filter (cutoff 500 nm) was inserted in the optical path after the collection objective to remove higher diffracted orders.…”

Influence of the substrate material on the knife-edge based profiling of tightly focused light beams

“…In this context, it is known that the resonance behavior of, for instance, plasmonic particles is influenced drastically in case of a dielectric interface being placed in close proximity (see for instance [16][17][18]). We now study the influence of the substrate material on the knife-edge profiling scheme in detail by performing knife-edge measurements for different detector and substrate materials.…”