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How 34,000 tiny holes might thwart a counterfeiter

07 July 2015

Scientists working in Singapore have found a method that might potentially prevent counterfeit in currency, documents, credit cards and ID cards.

Many modern documents include holograms to enhance their security (image: Shutterstock)

Many modern documents include holograms to enhance their security, and they are generally difficult to replicate outside of an optical lab. Although accurate recreation of these holograms is extremely challenging, a similar shiny, multi-coloured look can be created using a mixture of pigments and base, and this may pass a quick inspection.

The new technology, developed by a team at the National University of Singapore, aims at higher-level security measures rather than street-level counterfeiting. The team has designed an 'ultra-capacity nano-photon sieve' - a device with the capacity to incorporate more than 34,000 'nanoholes' (~300nm in diameter) randomly distributed in its surface. The feature enables the display of a high-pixel and high-quality holographic image at a controlled position.

“Highly secured virtual information is stored in the collection of these nanoholes and they can only be retrieved and read at a particular distance when a proper polarized illumination is employed,” says Qiu Chang-Wei, an assistant professor at the National University of Singapore.

“Our device can be customised for various applications as the dimensionality - for example, two-dimensional or three-dimensional - display distance, polarization, and wavelength dependence can be tailored according to needs.”

“We are looking into making our system more robust, developing multiple holographic images at multiple displaying planes, wavelength-dependent, or polarization-dependent three-dimensional images, higher pixels, and other emerging applications enabled by the capability of handling such a huge quantity of nanoholes,” says Qiu.

An article describing this work is published in the journal, Nature Communications.

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