Until now, light diffusing materials have either diffused light by embedding minute scatterers, or bent light by refraction due to minute irregularities on the surface.However, scatterers do not have both ``brightness'' and ``angular spread,'' and refractors have drawbacks such as insufficient ``angular spread'' and are easy to get dirty, so there has been no material that satisfies all of the above.

　The Morpho butterfly is a shining blue butterfly that is native to South America and is also called a living jewel.The research took advantage of the fact that the Morpho butterfly's wings have bright, wide-angle, uniformly colored reflections, and are also water repellent.A manufacturable structure was designed using electromagnetic field simulation, and was manufactured using semiconductor technology.

　This sheet has a high transmittance (approximately 90%) and has antifouling properties because the nano-irregularities on its surface have the same water-repellent effect as a lotus leaf (lotus effect).The angular spread is sufficient at ±40° from the vertical direction, and there is no chromatic dispersion.Furthermore, depending on the design, it is also possible to control the shape anisotropy of the diffused light.

　This time, the research group devised a structure that satisfies all the requirements of ``bright, wide-angle, unbiased color, and has antifouling properties'' by applying the unique reflective properties of the morpho butterfly to transmission. It was confirmed.It is hoped that this will lead to applications such as daylight windows that help save energy and light diffusion sheets that are useful for various types of lighting.

Paper information:【Advanced Optical Materials】Development of a High-Performance, Anti-Fouling Optical Diffuser Inspired by Morpho Butterfly's Nanostructure