Abstract
Morpho butterflies are well-known for their iridescence originating from nanostructures in the scales of their wings. These optical active structures integrate three design principles leading to the wide angle reflection: alternating lamellae layers, "Christmas tree" like shape, and offsets between neighboring ridges. We study their individual effects rigorously by 2D FEM simulations of the nanostructures of the Morpho sulkowskyi butterfly and show how the reflection spectrum can be controlled by the design of the nanostructures. The width of the spectrum is broad (≈ 90 nm) for alternating lamellae layers (or "brunches") of the structure while the "Christmas tree" pattern together with a height offset between neighboring ridges reduces the directionality of the reflectance. Furthermore, we fabricated the simulated structures by e-beam lithography. The resulting samples mimicked all important optical features of the original Morpho butterfly scales and feature the intense blue iridescence with a wide angular range of reflection.
Highlights
Many insects feature resourceful structural colors [1,2,3,4,5,6]
We analyze the three design principles causing the wide angle reflection observed in blue Morpho butterflies: alternating lamellae layers, “Christmas tree” like shape, and offsets between neighboring ridges
Shortening the upper lamellae layers of the ‘simple’ structure results in an ‘inspired’ “Christmas tree” like structure but reduces the intensity to 60% compared to the simple structure
Summary
Many insects feature resourceful structural colors [1,2,3,4,5,6]. Especially the famous iridescence of Morpho butterflies has attracted the attention of researchers for a long time. Potyrailo et al [9], for example, revealed that the optical response of the nano-scale structures of the Morpho butterfly changes for different vapors. They suggested that mimicking of this feature might outperform existing photonic vapor sensors. We analyze the three design principles causing the wide angle reflection observed in blue Morpho butterflies: alternating lamellae layers, “Christmas tree” like shape, and offsets between neighboring ridges. We conclude that the combination of these three design principles is responsible for the famous wide angle reflection of blue light with high intensity observed in blue Morpho butterflies
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