Yoshioka Shinya, Kinoshita Shuichi
Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan.
Phys Rev E Stat Nonlin Soft Matter Phys. 2011 May;83(5 Pt 1):051917. doi: 10.1103/PhysRevE.83.051917. Epub 2011 May 18.
It is well known that the metal-like strong reflection observed in the elytra of some kinds of beetles is produced by multilayer thin-film interference. For the quantitative analyses of the structural colors in these elytra, it is necessary to know accurate values of the refractive indices of the materials that comprise the multilayer structure. However, index determination is not an easy task: The elytron surface is not flat but curved and usually contains many irregular bumps, which cause scattering loss. These structural characteristics prevent us from directly applying conventional optical techniques for index determination, such as ellipsometry, since these techniques require a perfectly specular surface. In this paper, we report a new experimental procedure that can directly determine the refractive indices of individual layers in natural multilayer systems. This procedure involves semi-frontal thin-sectioning of the sample and subsequent optical examinations using a microspectrophotometer. We demonstrate that the complex refractive index and its wavelength dependence can be successfully determined for one kind of beetle.
众所周知，在某些甲虫的鞘翅中观察到的类似金属的强反射是由多层薄膜干涉产生的。为了对这些鞘翅中的结构色进行定量分析，有必要知道构成多层结构的材料的准确折射率值。然而，折射率的测定并非易事：鞘翅表面不是平的，而是弯曲的，并且通常包含许多不规则的凸起，这会导致散射损失。这些结构特征使得我们无法直接应用传统的光学技术来测定折射率，比如椭圆偏振光谱法，因为这些技术需要一个完美的镜面表面。在本文中，我们报告了一种新的实验方法，该方法可以直接测定天然多层系统中各层的折射率。这个方法包括对样品进行半正面薄切片，然后使用显微分光光度计进行光学检查。我们证明，对于一种甲虫，可以成功地测定其复折射率及其与波长的关系。
