Randomness in highly reflective silver nanoparticles and their localized optical fields

TL;DR

This paper demonstrates a large-area near-infrared reflector made of randomly distributed silver nanoparticles, highlighting the importance of geometrical randomness in localizing optical near-fields and enhancing reflection.

Contribution

It reveals that geometrical randomness, rather than resonant coupling, is key to localized optical fields in silver nanoparticle reflectors, supported by rigorous electromagnetic theory.

Findings

Random silver nanoparticle arrays achieve high near-infrared reflection.

Geometrical randomness causes particle-dependent localization of optical near-fields.

Theoretical analysis clarifies the role of randomness in near-field processes.

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.