The wings of a butterfly are a thing of beauty as they shimmer and dance in the breeze.They are also a marvel of light-directing properties. Researchers have discovered that the swallowtail butterfly of eastern and central Africa, Papilio nireus, has fluorescent wings that reflect and direct light in much the same way that the modern light-emitting diodes in high-end computer screens and televisions do.
Pete Vukusic and Ian Hooper of Exeter University in England studied the colored parts of the swallowtail's wings and found that the scales that comprised them contain photonic crystals whose atoms are spaced so precisely that only certain wavelengths of light can pass through. The crystals are also saturated with fluorescent pigments that help them create specific wavelengths of light, visible to us as bright colors.
Tiny, mirrorlike structures known as distributed Bragg reflectors reflect this fluorescent light as well as all the other light the photonic crystal allows to pass through. The result: butterfly wings that transform ordinary sunlight into brilliant greens and blues incredibly efficiently.
Thus what the butterflies evolved to do, scientists have built light-emitting diodes to do, employing the exact same components--photonic crystals and Bragg reflectors--in search of ever better ways to project and direct light. The findings are published in the current issue of Science.