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Morpho-Butterfly-Inspired Patterning of Helical Photonic Structures for Circular-Polarization-Sensitive, Wide-Angle Diffuse Reflection

ABSTRACT

Cholesteric liquid crystals are known to exhibit a circular-polarization selective Bragg reflection band over a wavelength region determined by their reflective index and pitch. In a planar device where the molecules are aligned unidirectionally at the substrate surface, cholesteric liquid crystals act as flat dielectric mirrors, reflecting light at an angle fulfilling the law of reflection. Here, it is shown that by introducing a random structure inspired by the Morpho didius butterfly into the distribution of the helix phase, the reflected light phase becomes randomized, leading to a diffuse reflection that spans over an angle greater than ±30°. The reflection maintains its circular polarization selectivity, making these materials unique compared to the butterfly itself and other man-made structures mimicking the butterfly's structure.