Tiny spirals could prevent identity theft

NASHVILLE, June 3 (UPI) -- Spirals the size of a dime, shrunk down six million times, may be the next secure method of tracking and guarding information because they are almost impossible to counterfeit.

Researchers at Vanderbilt University created tiny, gold Archimedes spirals, shrank them down, and found they reacted uniquely to infrared and polarized light, leading to the thought of using them for security.

"If nano-spirals were embedded in a credit card or identification card, they could be detected by a device comparable to a barcode reader," said Richard Haglund, Ph.D., a professor of physics at Vanderbilt University, in a press release.

The spirals were shrunk to sizes smaller than wavelengths of visible light and when illuminated with infrared light glow blue. This is effect, called frequency doubling or harmonic generation, happens when the infrared light is absorbed by the gold electrons, which are forced to move along the spiral, driven toward the center with enough energy to emit blue light at double the frequency of infrared.

The reaction to polarized light was similar, with circularly polarized light maximizing the blue light produced by the spirals and counter-clockwise polarized light producing a minimal amount of blue light.

The spirals are thought to be so secure because a square array with 100 nano-spirals on it is invisible to the naked eye, and an array could be placed in a secret location on a credit card, ID or other form of identification.

The study is published in Nanophotonics.