The iridescence of disordered resonant metasurfaces

Résumé : Due to the intrinsic limitations of pigment coloration, the generation of bright, largely tunable, and angle-insensitive colors with nanostructured surfaces has received considerable interest. However, coatings that exhibit diffuse color changes with the viewing and illumination directions are also important as they provide extra degrees of freedom to create attractive visual effects. Here, we present metasurfaces composed of a non-close packed assembly of metallic nanoparticles deposited on a reflective substrate coated with a low-index spacer. This geometry, which combines plasmonic and Fabry-Perot resonances, offers uncommon iridescences, differing from those classically observed with natural nanostructures or thin-film interferences. We highlight a remarkable iridescence with only two distinct colors and theoretically investigate its origin with an intuitive and accurate model that unveils the rich physical mechanisms at play. The interpretation paves the way towards the design of easy-to-make and universal building blocks with a large resilience to fabrication imperfections, and great potential for innovative coatings and fine-art applications.