Assembling and Modeling Stacked Disordered Metasurfaces

TL;DR

This paper presents a novel lithography-free method to create stacked disordered metasurfaces, models their complex scattering behavior, and demonstrates a color-changing encryption device based on illumination conditions.

Contribution

It introduces a new fabrication approach for disordered metasurfaces, develops accurate models for their scattering properties, and demonstrates a practical application in chromo-encryption.

Findings

Accurate angle-resolved reflection models for disordered metasurfaces.

Coherent illumination significantly alters perceived color of diffuse scattering.

A centimeter-scale chromo-encryption device demonstrating color change with illumination.

Abstract

Disordered metasurfaces offer unique properties unattainable with periodic or ordered metasurfaces, notably the absence of deterministic interference effects at specific wavelengths and angles. In this work, we introduce a lithography-free nanofabrication approach to realize cascaded disordered plasmonic metasurfaces with sub-micron total thickness. We experimentally characterize their angle-resolved specular and diffuse reflections using the bidirectional reflection distribution function (BRDF) and develop accurate theoretical models that remain valid even at large incidence angles. These models reveal the intricate interplay between coherent (specular) and incoherent (diffuse) scattering and demonstrate how coherent illumination can strongly influence the perceived color of diffusely scattered light. Exploiting this effect, we realize a centimeter-scale chromo-encryption device whose color changes depending on whether it is viewed under direct or diffuse illumination. Our results lay the groundwork for advanced nanophotonic platforms based on stacked disordered metasurfaces, offering versatile optical functionalities inaccessible with traditional multilayer thin-film technologies or single-layer metasurfaces.