Shang Guoliang, Maiwald Lukas, Renner Hagen, Jalas Dirk, Dosta Maksym, Heinrich Stefan, Petrov Alexander, Eich Manfred
Institute of Optical and Electronic Materials, Hamburg University of Technology, Eissendorfer Strasse 38, 21073, Hamburg, Germany.
Institute of Solids Process Engineering and Particle Technology, Hamburg University of Technology, Denickestrasse 15, 21073, Hamburg, Germany.
Sci Rep. 2018 May 17;8(1):7804. doi: 10.1038/s41598-018-26119-8.
Non-iridescent structural colors based on disordered arrangement of monodisperse spherical particles, also called photonic glass, show low color saturation due to gradual transition in the reflectivity spectrum. No significant improvement is usually expected from particles optimization, as Mie resonances are broad for small dielectric particles with moderate refractive index. Moreover, the short range order of a photonic glass alone is also insufficient to cause sharp spectral features. We show here, that the combination of a well-chosen particle geometry with the short range order of a photonic glass has strong synergetic effects. Using a first-order approximation and an Ewald sphere construction the reflectivity of such structures can be related to the Fourier transform of the permittivity distribution. The Fourier transform required for a highly saturated color can be achieved by tailoring the substructure of the motif. We show that this can be obtained by choosing core-shell particles with a non-monotonous refractive index distribution from the center of the particle through the shell and into the background material. The first-order theoretical predictions are confirmed by numerical simulations.
基于单分散球形颗粒无序排列的非虹彩结构色，也称为光子玻璃，由于反射率光谱的逐渐过渡而呈现低色彩饱和度。由于具有中等折射率的小介电颗粒的米氏共振较宽，通常无法通过颗粒优化实现显著改善。此外，仅光子玻璃的短程有序也不足以产生尖锐的光谱特征。我们在此表明，精心选择的颗粒几何形状与光子玻璃的短程有序相结合具有强大的协同效应。使用一阶近似和埃瓦尔德球构造，此类结构的反射率可与介电常数分布的傅里叶变换相关联。通过定制图案的子结构可实现高饱和颜色所需的傅里叶变换。我们表明，这可以通过选择从颗粒中心穿过壳层并进入背景材料具有非单调折射率分布的核壳颗粒来实现。一阶理论预测得到了数值模拟的证实。
