An investigation of optical absorptions by periodic structures on cuticles of insects

本项目的目的是研究存在于昆虫表皮上的周期性结构对光的吸收。在项目实施过程中，我们进行了以下几方面的研究.昆虫角膜的显微镜观察据报道，某些夜蛾的角膜前表面覆盖有微小的乳头，其远小于可见光的波长，并以六边形阵列排列（Acta Physiological Scandinavia Vol.63. P.19）。通过扫描电子显微镜对许多昆虫的角膜进行观察，发现有些蝶科和灰蝶科的蝴蝶也有类似夜蛾的乳头阵列。蝴蝶的角膜乳头的形状是圆柱体，其直径和高度（振幅）分别约为0.1和0.2微米。接头的中心到中心的间距也为约0.2微米。应该注意的是，角膜可以被认为是乳头阵列的周期性结构。计算机模拟我们认为昆虫角膜乳头的光学功能可能与光学器件中常见的周期性结构有关。因此，我们在微观观察的基础上构建了乳头阵列的周期性结构模型。我们发展了一种分析周期结构模型光衍射的数值算法。我们评估的反射率和透射率的周期性结构模型在可见光区从计算机模拟。该算法同样适用于周期结构对光的共振吸收的数值分析.实验研究了用显微镜测量昆虫角膜微小区域反射率和透射率的方法。我们还测量了角膜的折射率的浸泡法。

The aim of this project is to investigate absorption, of light by periodic structures that exist on cuticles of insects. In the term of project, we have carried on the following studies.1. Microscopic observation of insect corneas It has been reported that the front surface of corneas of a certain night moth is covered with minute nipples, which is much smaller than a wavelength of visible right and arranged in hexagonal array (Acta Physiological Scandinavia Vol.63. P.19). We observed corneas of numerous insects through a scanning electron microscope and found that some butterflies of Morphidae or Lycaenidae also have the nipple array on the surface of their corneas likewise a night moth. The shape of the cornea nipples of the butterflies is a circular cylinder and its diameter and height (amplitude), respectively, are about 0.1 and 0.2 micrometer. The center-to-center spacing of the nipples is also about 0.2 micrometer. It should be noted that the corneas could be considered as periodic structures of the nipples array.2. Computer simulation We suppose that the optical functions of the insect corneas nipples may be associated with those periodic structures that are familiar with optical devices. We therefore constructed a periodic structure model of the nipples array on the basis of the microscopic observation. We have developed a numerical algorithm for analyzing diffraction of light from the periodic structures model. We evaluate reflectance and transmittance of the periodic structure models over the visible region from computer simulation. The algorithm can be also applicable to the numerical analysis of resonance absorptions of light by periodic structures.3. Experiment We have investigated a measurement of reflectance and transmittance at the minute region of insect corneas by the microspectrophotmetric experiment. We also measured refractive indices of corneas by the immersion method.