Harmony of order and disorder in photonic nanostructures inspired by morpho structure

Abstract

Morpho butterfly shows metallic and shimmering blue. This blue comes from multilayered ridges on scales of wings of Morpho butterfly, so Morpho blue is structural color generated from their photonic nanostructure. Structural color generally depends on viewing angle, but Morpho blue still shows stable blue against viewing angle change. This unusual characteristic comes from order and disorder nanostructures of Morpho butterflies, and especially random arrangement in multilayered ridges is mainly related to angle-independent property. By the way, strictly speaking, less changed structural color is more correct expression to describe Morpho blue than angle-independent or stable structural color. In this thesis, main subject is repro-ducing structural color of Morpho butterfly. Meanwhile, material is also important to consider quality of structural color, so material effects are calculated by using refractive index. As a result, chitin and air of Morpho butterfly can makes structural color with high color purity and stable color with low angle independence. Unfortunately, chitin and air can’t be used in fabrication process, so Cr for absorption and TiO2 / SiO2 two dielectric materials are used in this thesis. In order to generate randomness in structure, particularly in height of multilayer, silica spheres of various sizes are distributed in monolayer, and then thin film is deposited on the silica spheres. Additionally, it is proven that the effect of silica spheres of various sizes is related to angle-independent structural color. Optical performance is evaluated after fabrication, and then the fabricated film shows better color purity and color stability compared to real Morpho butterflies. The measured results are discussed on color space again, and it is found that resolution of human eyes is also related to constant structural color of Morpho butterfly, because too small variation can’t be distinguishable. These fabricated films can be detached by polymer en...