Among the natural creatures that have structural colors, the Morpho butterfly is one of the most remarkable species because its blue color displays both a high reflectivity from interference and a low angular dependence. The origin of this unique coloration is thought to be a specific three-dimensional nanostructure with order and disorder that prevents the rainbow color. More importantly, the artificial Morpho-color has been successfully realized in spite of the lack of vertical randomness. Thus, we have recently studied the optical role of in-plane randomness using a numerical simulation, and revealed that the three-dimensional randomness can be replaced by a two-dimensional randomness. However, the details of the simulation methodology and its validity were not explicitly discussed. In this paper, we report the three-dimensional simulation method for analyzing the optical properties of non-periodic structures such as the Morpho butterfly. Moreover, the effect of light incoherence on the Morpho-coloration is evidently shown.
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