Colour characterization of a Morpho butterfly wing-scale using a high accuracy nonstandard finite-difference time-domain method
Colour characterization of a Morpho butterfly wing-scale using a high accuracy nonstandard finite-difference time-domain method
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DOI：
10.1016/j.micron.2006.07.004
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发表时间：
2007-01-01
期刊：
影响因子：
2.4
通讯作者：
Yatagai, Toyohiko
中科院分区：
文献类型：
--
作者：
Banerjee, Saswatee;Cole, James B.;Yatagai, Toyohiko
在某些种类的飞蛾和蝴蝶中，彩虹色是由亚波长衍射结构产生的。这种结构的光学特性很大程度上取决于照明辐射的波长、入射角和偏振状态以及视角。这种结构只能通过求解麦克斯韦方程组来分析，但由于只有少数简单、高度对称的结构存在解析解，因此必须采用数值方法。我们通过使用高精度版本的非标准有限差分时域算法模拟尺度结构，研究了蝴蝶翅膀的二维光学特性。模拟结构是计算机生成的模型，是在大闪蝶翅膀的单鳞片横截面的透射电子显微 (TEM) 图像中观察到的树状结构的某种准周期排列的模型。我们假设该结构由稍有损耗的介电材料制成。我们通过计算无限圆柱体产生的散射场强度来检查我们方法的准确性和有效性，并将结果与使用米氏理论的分析计算进行比较。接下来，我们通过计算垂直入射时鳞片的反射率和透射率光谱，并与实验测量进行比较，推导出大闪蝶翅膀上的地面鳞片的真实折射率和吸收系数与波长的关系。最后，我们根据标尺的远场反射率和透射率光谱计算了不同观察方向的三刺激值和相应的颜色坐标，以表征其显色能力。 (c) 2006 Elsevier Ltd. 保留所有权利。
In certain species of moths and butterflies iridescent colours arise from subwavelength diffractive structures. The optical properties of such a structure depend strongly on wavelength, incidence angle and state of polarization of illuminating radiation and on the viewing angle. Such structures can be analyzed only by solving Maxwell's equations, but since analytical solutions exist for only a few simple, highly symmetric structures numerical methods must be employed. We investigated the optical properties of butterfly wings in two dimensions by simulating a scale structure using a high accuracy version of nonstandard finite-difference time-domain algorithm. The simulated structure is a computer-generated model of a certain quasi-periodic arrangement of tree-like structures observed in the transmission electron micrograph (TEM) image of a transverse cross-section of a single scale from Morpho butterfly wings. We assumed that the structure is made of a slightly lossy dielectric material. We checked the accuracy and validity of our approach, by computing scattered field intensities due to an infinite cylinder and compared the results with analytical calculations using Mie theory. Next we deduced the wavelength dependence of a real refractive index and an absorption coefficient for the ground scales on the wings of Morpho sulkowskyi butterfly by computing the reflectivity and transmissivity spectrum of a scale at normal incidence, and comparing with experimental measurements. Finally, we calculated the tristimulus values and corresponding colour coordinates for various viewing directions from the scale's far-field reflectivity and transmissivity spectra to characterize its colour rendering abilities. (c) 2006 Elsevier Ltd. All rights reserved.