Biological Structure, Color And Artificial Structure Color Study

When the band gap original by the period structure located in visible region, because the light with wavelength falling into the band gap can not traveling in the structure, producing reflectance peak, so this structure will present the color of the light whose wavelength corresponding the region of the band gap. If there are two or more reflectance peaks original by band gap or other reasons in visible region, there will be mix color.Color production in nature takes advantage of either structure coloration and pigmentation. Structure colors in insects and bird feathers have been usually qualitatively understood by thin-film interference, diffraction, scattering and also photonic crystals structure.In the first chapter, the introduction of basic knowledge of coloration is given. The background knowledge and the main research progress of photonic crystals and biological structure color are introduced.In the second chapter, commonly used theretical methods of PCs are introduced. Plan wave method and transfer matrix method are discussed in detail. Calculating RGB values by the trustimulus function by CIE is shown lastly.In the third chapter, we studied the mechanism of the coloration of the eye pattern on peacock tail feathers. We found that the color is come from the two-dimensional photonic crystals structure around the scarfskin of the barbules. Peacock controls the location of the band gap, viz. the mail reflectance peak, through changing the lattice constant of the two-dimensional photonic crystals structure, and tries to buildup the influence of the Fabry-Perot interference peak through changing the number of periods, therefore producing the mix brown color.In the fourth chapter, we studied the iridescence phenomena of the green and purple feathers on the neck of pigeon. The structure and optical spectrum suggest that the iridescence phenomena in both green and purple barbules should be due to interference from the top keratin cortex layer alone. Furthermore, we also studied theoretically the influence of light polarization on coloration. With varying incident angle, the changes in both color and brightness are different for different polarizations. The existence of Brewster's angle for p-polarization plays an important role on colouration.In the fifth chapter, base on the two-dimensional photonic crystals structure on the peacock tail feathers, we studied the mechanism of the brown color on the eye pattern in details. Furthermore, we discussed the condition of one-dimensional, simple two-dimensional and three-dimensional in brief. These will be beneficial to the attempts of artificial coloration.