Structural integration design for enhanced photoluminescence in butterfly scales

Here we present a structural integration design in butterfly scales that helps to enhance the photoluminescence of the scale pigment. The optical mechanism lying behind blue scales of the butterfly Papilio oribazus and green ones from Papilio nireus is illustrated through respective detailed investigation. Microscopic characterization reveals a nano-scaled optical architecture comprised of a network on top of a two-dimensional (2D) photonic crystal slab (PCS) and a multilayer structure located under the PCS. The top side of the PCS is infused with pigments. Combining the experimental reflection spectra and computational simulation through finite difference time domain (FDTD) and plane wave expansion (PWE) methods, we find that the network acts as an antireflection layer harvesting UV excitation light for the pigment, and the 2D PCS works as a light filter and waveguide, functioning together with the multilayer structure to extract needed light from the pigment emission and guide it out of the scales. This finding provides a working prototype to enrich the horizon for the design of sophisticated optical devices with high functionality.