"It's just amazing," said optics researcher Pete Vukusic of Exeter University in the UK. "We got to it one way and nature got to it another way."
Only nature did it 30 million years earlier, he added. Vukusic and his colleague Ian Hopper have a short paper on the discovery in the Nov. 18 issue of
Science.
In the case of manufactured LEDs, it's electricity that makes the light, which is then controlled by photonic crystals.
In butterflies, sunlight makes the colored light by being used in two ways: first by pigments that reflect only the desired color; second by fluorescent pigments absorbing other wavelengths of light to power up emission of the same preferred color.
What makes LEDs and butterfly wings so strikingly similar is that both use photonic crystals to control where the light goes. Artificial photonic crystals are usually made in neat arrays, using silica.
Butterflies grow photonic crystals like hair or fingernails, said Vukusic. Once grown, they are no longer living tissue and they continue to work long after a butterfly is dead and pinned in a sample case.
As for why swallowtails need to be so extraordinarily flashy — the function seems to be for territorial signaling to other butterflies of the same species, said Vukusic.
Other researchers have found that the butterflies have receptors in their eyes for the same colors they flash.
So by reflecting, fluorescing and aiming that color with photonic crystals, butterflies are just sending light signals as loudly and clearly as they can.
"It's showing us what a biological system can do," said Helen Ghiradella of State University of New York at Albany.
Ghiradella has studied how fireflies make use of color which are of exactly the same wavelength they see best.
"(These butterflies) show a control of light that is absolutely unbelievable," said Ghiradella.
