Demonstration of a diffraction-based optical diffuser inspired by the Morpho butterfly.

Optical diffusers are widely used in a variety of light sources to create uniform illumination over a wide field of view. Inspired by the diffraction-based light diffusion of the Morpho butterfly, here we demonstrate a novel diffuser which fulfils (i) high transmittance, (ii) wide angular spread, and (iii) low color dispersion. Two-dimensional nanopatterns were designed using optical simulations to enable simple fabrication. By introducing anisotropy into the surface nanopatterns, we achieved control of anisotropic light diffusion, which has been challenging for conventional diffusers. Next, the designed diffuser was implemented over a large area (100 × 100 mm2) via nanoimprint lithography. The obtained diffuser demonstrated a high transmittance of ∼85% and full width at half maximum (FWHM) of >60° with low color dispersion, outperforming conventional diffusers. Since the presented diffuser has the controllable diffusion properties with low light loss, it has many applications including LED lighting, displays, and daylight harvesting systems.