Optimization of sharp and viewing-angle-independent structural color

TL;DR

This paper presents a numerical optimization approach to design structural colors that are both spectrally sharp and viewing-angle-independent, overcoming previous limitations of narrow bandwidth and broad angle properties.

Contribution

The study introduces a novel optimization method to create geometries with simultaneous narrow bandwidth and broad viewing angle in structural colors.

Findings

Achieved 7% bandwidth in scattering

Peak wavelength varies less than 1% over angles

Peak height and width vary less than 6% over angles

Abstract

Structural coloration produces some of the most brilliant colors in nature and has many applications. However, the two competing properties of narrow bandwidth and broad viewing angle have not been achieved simultaneously in previous studies. Here, we use numerical optimization to discover geometries where a sharp 7% bandwidth in scattering is achieved, yet the peak wavelength varies less than 1%, and the peak height and peak width vary less than 6% over broad viewing angles (0--90$^\circ$) under a directional illumination. Our model system consists of dipole scatterers arranged into several rings; interference among the scattered waves is optimized to yield the wavelength-selective and angle-insensitive response. Such designs can be useful for the recently proposed transparent displays that are based on wavelength-selective scattering.