Vanderbilt University researchers have developed nano-spirals with unique optical properties they say would be almost impossible to counterfeit if they were embedded into identity cards, currency, and other important materials.
The researchers built the tiny spirals and used ultrafast lasers to characterize their optical properties. Unlike other nano-spirals, the new spirals have solid arms and are much smaller, as a square array with 100 of the Vanderbilt-developed nano-spirals on a side is less than a hundredth of a millimeter wide.
Spirals this small have unusual optical properties--for example, when they are illuminated with infrared laser light, they emit visible blue light. In addition, when struck by a polarized light beam, the amount of blue light the nano-spirals emit varies as the angle of the plane of polarization is rotated through 360 degrees.
The researchers found when left-handed nano-spirals are illuminated with clockwise polarized light, the amount of blue light produced is maximized because the polarization pushes the electrons toward the center of the spiral. Conversely, counterclockwise polarized light produces a minimal amount of blue light. These unique characteristics could be used to make a customizable signature that would be extremely difficult to counterfeit, according to the researchers.
From Research News @ Vanderbuilt
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