Optical properties of the micro/nano structures of Morpho butterfly wing scales

The micro/nano structures of the wing scales in Morpho butterfly are responsible for the structural coloration, with a major part ascribed to interference and diffraction of light. The optical properties of the butterfly wings were investigated by simulating a two-dimensional model using rigorous coupled-wave analysis technique. It is proved that they depend strongly on the structural parameters, incidence angle and refractive index. The peak value and the peak wavelength of the reflection efficiency increase as the vertical periodic thickness increases. The peak value decreases observably, while both of the bandwidth and the peak wavelength increase when the number of the vertical periods decreases. Increase of the horizontal periodic width causes a decrease of the peak value and an increase of the peak wavelength, although the variations are small. The peak value decreases distinctly and the peak wavelength increases as the ambient refractive index increases, which corresponds to the variation in ambient conditions. The research reveals the mechanisms of the brilliant structural color in Morpho butterfly, and is of great significance to the design, manufacture and applications of the bionic micro/nano structures for gas detection.