Analysis and fabrication of optical active nanostructures inspired by the blue Morpho butterfly

Blue Morpho butterflies are well-known for their blue irradiance. This famous blue reflection originates from nanostructures in the scales of their wings. These optical active structures integrate three design principles leading to the wide angle reflection: alternative lamellae layers, Christmas tree like shape, and zigzag pattern of the ridges. In order to study their individual effects rigorously, 2D FEM simulation of the nanostructures of Morpho sulkowskyi was used to calculate their reflection spectrum. The reflection spectrum is found to be broad (~ 90 nm) for alternating layers and can be controlled by varying the design pattern. The Christmas tree like pattern helps to reduce the directionality of the reflectance. These structures were exactly fabricated by e-beam lithography . Each type covered an area of 500 μm × 500 μm. In contrast to the original butterfly structures they lay flat on the substrate with a height of 200 nm but mimic already all important features of the original Morpho butterfly (Christmas tree like structure with alternating lamellae and offsets between the trees). It is found that our new samples maintain the intense blue characteristics with a wide angular range of reflection (± 25°).