Peacock feathers work like lasers

Spektrum der Wissenschaft

6.8.2025

Translation: machine translated

Blue peacocks are considered to be very magnificent birds: their tail feathers are particularly impressive. Now it turns out that they also have special physical properties.

Male peacocks use bright colours and an impressive wheel of raised tail feathers to attract females - a spectacle in itself. But the bright colours of the tail feathers conceal a previously unknown detail: Tiny, reflective structures can focus incoming light like a laser, reports a team led by Anthony Fiorito III from Florida Polytechnic University in Lakeland.

Laser beams are created when a medium (often a dye) is excited with energy, which raises the electrons in the atoms of the medium to a higher energy level. If these particles then fall back into lower energy states, they emit their energy again in the form of photons. The special feature: The light quanta all have the same wavelength and can in turn cause excited atoms in the medium to also emit photons. In a laser, the emitted photons are reflected back and forth by mirrors in a cavity, which amplifies the light beams and creates a focussed laser beam of a specific wavelength.

Fiorito III and his team were able to realise a similar process with peacock feathers: They soaked the eyespots of the tail feathers regularly in a dye solution and then irradiated them with a light source. The structure of the feathers forms a reflective cavity that bounces the light back and forth, focussing it into a beam. As a result, the feathers emitted tiny beams of yellow-green laser light, which the scientists were able to detect. However, these rays cannot be seen with the naked eye and are emitted at two different wavelengths.

The researchers were surprised that differently coloured areas of the peacocks' eyespots emitted the same wavelength, as they are likely to differ in their microstructure. Whether the laser light plays a role in courtship is still unclear: birds' eyes can perceive light spectra that the human eye does not recognise. The extent to which this also applies to laser light has yet to be tested.

In any case, the bright blue and green of the animals is due to so-called structural colours and is not caused by pigments embedded in feathers. Ordered microstructures in the feathers reflect the light in certain wavelengths and, in addition to the colourfulness, also provide the characteristic iridescence of the animals, which also fascinates human observers.

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