Near-Field Effects at the Nodes of a Gold Nanonetwork Grown by Laser Ablation in Superfluid Helium: Crossover between “Tip and Gap Hot Spots”

The development of new methods for the synthesis of nanosystems with plasmonic properties and for their analysis is an important field of modern photonics. Here, low-temperature laser synthesis of quasi-two-dimensional gold nanonetworks (with individual nanowire diameters of 5 nm) is carried out in superfluid helium. The plasmonic properties of nanosystems obtained in this way are investigated by Raman scattering for the first time. Possible features of the near field in these systems are studied using three-dimensional numerical electrodynamic modeling by the finite element method in the visible to near-infrared spectral range (400–1000 nm). The complex internal structure of hot spots arising around two intersecting 5-nm nanowires (the elementary model unit) and the diversity of their localization types, showing tip-to-gap transition, are demonstrated.