A recent study published in the journal Scientific Reports highlights a fascinating property of peacock feathers: they can emit laser light when subjected to multiple dyeing processes. This discovery marks the first instance of a biolaser cavity identified in the animal kingdom, according to the authors of the paper.
The vibrant iridescence seen in peacock feathers and butterfly wings originates not from pigments, but from their structural composition. In butterfly wings, for example, scales made of chitin are arranged in a pattern reminiscent of roof tiles. These structures function as a diffraction grating, where photonic crystals yield specific colors or wavelengths of light, unlike a traditional diffraction grating that reveals the entire light spectrum, similar to a prism.
For peacock feathers, the bright colors are produced by the ordered arrangement of melanin rods within the barbules, which are fibrous components coated in keratin. The variances in color correlate with the distances between these barbules.
These natural phenomena exemplify what physicists classify as photonic crystals, also referred to as photonic bandgap materials. Such crystals are “tunable,” meaning they possess an intricate ordering that selectively blocks certain wavelengths of light while allowing others to pass. By modifying the structure, such as resizing the tiles, the crystals can be adjusted to respond to different wavelengths. For instance, the rainbow weevil can manipulate its scale size and the amount of chitin utilized to fine-tune its color display.
In addition, the color perception remains constant regardless of the viewer’s angle. The scales serve dual purposes, offering both aesthetic appeal and protection against environmental elements. There are various synthetic photonic crystals available, but a deeper understanding of these naturally occurring structures could pave the way for innovative materials with similar characteristics. Potential applications include iridescent windows, self-cleaning surfaces for automobiles and buildings, or even waterproof fabrics. Additionally, paper currency could integrate encrypted iridescent designs to combat counterfeiting.
