Modelling structural colour from helicoidal multi-layer thin films with natural disorder

A coupled mode theory based on Takagi-Taupin equations describing electromagnetic scattering from distorted periodic arrays is applied to the problem of light scattering from beetles. We extend the method to include perturbations in the permittivity tensor to helicoidal arrays seen in many species of scarab beetle and optically anisotropic layered materials more generally. This extension permits analysis of typical dislocations arising from the biological assembly process and the presence of other structures in the elytra. We show that by extracting structural information from transmission electron microscopy data, including characteristic disorder parameters, good agreement with spectral specular and non-specular reflectance measurements is obtained. (c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

In this study, a coupled mode theory based on Takagi-Taupin equations is applied to the analysis of light scattering from beetles. The method is extended to include perturbations in the permittivity tensor, allowing for the study of helicoidal arrays in scarab beetles and optically anisotropic layered materials. By extracting structural information from transmission electron microscopy data, including characteristic disorder parameters, the authors achieve good agreement with spectral specular and non-specular reflectance measurements.