6 September 2017 Light scattering optimization of chitin random network in ultrawhite beetle scales
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Abstract
Among the natural white colored photonics structures, a bio-system has become of great interest in the field of disordered optical media: the scale of the white beetle Chyphochilus. Despite its low thickness, on average 7 μm, and low refractive index, this beetle exhibits extreme high brightness and unique whiteness. These properties arise from the interaction of light with a complex network of chitin nano filaments embedded in the interior of the scales. As it’s been recently claimed, this could be a consequence of the peculiar morphology of the filaments network that, by means of high filling fraction (0.61) and structural anisotropy, optimizes the multiple scattering of light. We therefore performed a numerical analysis on the structural properties of the chitin network in order to understand their role in the enhancement of the scale scattering intensity. Modeling the filaments as interconnected rod shaped scattering centers, we numerically generated the spatial coordinates of the network components. Controlling the quantities that are claimed to play a fundamental role in the brightness and whiteness properties of the investigated system (filling fraction and average rods orientation, i.e. the anisotropy of the ensemble of scattering centers), we obtained a set of customized random networks. FDTD simulations of light transport have been performed on these systems, observing high reflectance for all the visible frequencies and proving the implemented algorithm to numerically generate the structures is suitable to investigate the dependence of reflectance by anisotropy.
Conference Presentation
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Francesco Utel, Lorenzo Cortese, Lorenzo Pattelli, Matteo Burresi, Silvia Vignolini, Diederik Wiersma, "Light scattering optimization of chitin random network in ultrawhite beetle scales", Proc. SPIE 10367, Light in Nature VI, 1036709 (6 September 2017); doi: 10.1117/12.2274447; https://doi.org/10.1117/12.2274447
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