Understanding and Exploiting the Optical Properties of Laser-Induced Quasi-Random Plasmonic Metasurfaces

Laser-induced structural colors have the potential for industrial implementation thanks to their versatility, efficiency, cost-effectiveness, and simplicity. However, the quasi-random nature of the nanoparticle (NP) distributions produced by lasers has made the understanding of their optical properties tricky and the confidence in their reproducibility limited. In this article, we demonstrate the potential of nanosecond lasers to control the diffraction, dichroism, and colors of random plasmonic metasurfaces while explaining the origin of their optical properties through electromagnetic simulations. The optical properties are first linked to the geometrical parameters of self-organized gratings that are induced by laser either on the surface by topographic modulation or below the surface by the growth of organized NPs. These two kinds of gratings are perpendicular to each other and exhibit different periods. The article unravels the main mechanisms that shape the spectral properties of these laser-induced NP gratings. Electromagnetic simulations evidence the role of hybrid resonances resulting from the far-field coupling of metallic NPs despite their size dispersion and relative disorder. They also demonstrate the impact of near-field coupling that leads to the hybridization of plasmonic modes of some particle pairs closely packed along the grating lines in these laser-induced structures. The article shows how the two kinds of self-organized gratings influence the diffraction and dichroism. Imperfections of laser-induced metasurfaces bring singular properties that do not exist in perfectly regular samples. They are used here to print faithful color images in different modes of observation and to use diffraction or dichroism as a security feature.