Randomness in highly reflective silver nanoparticles and their localized optical fields

Abstract

Reflection of near-infrared light is important for preventing heat transfer in energy saving applications. A large-area, mass-producible reflector that contains randomly distributed disk-shaped silver nanoparticles and that exhibits high reflection at near-infrared wavelengths was demonstrated. Although resonant coupling between incident light and the nanostructure of the reflector plays some role, what is more important is the geometrical randomness of the nanoparticles, which serves as the origin of a particle-dependent localization and hierarchical distribution of optical near-fields in the vicinity of the nanostructure. Here we show and clarified the unique optical near-field processes associated with the randomness seen in experimentally fabricated silver nanostructures by adapting a rigorous theory of optical near-fields based on an angular spectrum and detailed electromagnetic calculations.

Local circular polarizations in nanostructures induced by linear polarization via optical near-fields

“…. 7 Here, i indexes the nanostructures and ( ) In this paper, we extend our analysis to show that the dipoles induced in the nanostructures are actually circularly polarized by linearly polarized light irradiation. To understand this phenomenon, we analytically formulate the optical near-field interactions between two nanostructures, accounting for their polarizations and geometrical features.…”

“…First, we briefly review the silver nanoparticle-based NASIP device 5,6 and our former numerical analysis that highlighted the inherent structural randomness of this device. 7 Figure 1(a) shows a scanning electron microscope (SEM) image of the NASIP surface. The device exhibits high reflectance in the NIR regime while strongly transmitting visible and far-infrared light.…”

“…The elemental nanostructure is 120-150 nm in diameter and 10 nm thick and resonates at NIR wavelengths (centered around 1000 nm). [5][6][7] To characterize the detailed electromagnetic properties of the experimentally fabricated devices, we input the geometries of the fabricated silver nanoparticles to a numerical model comprising a vast number of voxels. Specifically, the SEM image shown in Fig.…”

“…NASIP, which comprises randomly distributed disk-shaped silver nanoparticles, highly reflects near-infrared (NIR) light and has been marketed as an energy-conserving device for cooling rooms during the summer months. [5][6][7] In our previous study, 7 we analyzed the structural randomness of the silver nanoparticles by electromagnetic calculations and a theory of optical near-fields based on an angular spectrum.…”

Dispersion‐Controlled Gold–Aluminum–Silicon Dioxide–Aluminum Nanopawn Structures for Visible to NIR Light Modulation

“…[ 42 ] For the numerical calculation of the reflectance and transmittance based on the full‐field formulation, a unit cell of the nanopawn structures with periodic boundary conditions along the x ‐ and y ‐axes and perfectly matched layers (PMLs) along the z ‐axis direction were used under normal incidence. [ 21,43–47 ] It was confirmed that the periodic boundary condition with randomly distributed multiple particles in the simulation window does not perturb the reflectance significantly, [ 21,43–47 ] by comparing simulations having larger simulation area (2 × 2 µm 2 ) (Figure S20, Supporting Information), different size of simulation window (periodicity) for single particle and multiple particles (Figure S21, Supporting Information), and different distribution of Au‐NPs (Figure S22, Supporting Information). From the scattered‐field formulation, the simulation domain was set as a spherical space surrounded by PMLs and use the scattering boundary condition to generate 50° oblique plane‐wave incidence.…”