Metasurface engineered to create three different images depending on illumination

Researchers have developed a metasurface device that can display three types of images depending on the illumination light. The three-channel device could be used as an anticounterfeiting measure or offer a new way to securely deliver encrypted information.

“Metasurfaces are artificial materials with tiny nanostructures that can be used to manipulate light,” said research team member Qi Dai from Wuhan University in China. “In this work, we exploited both the size and orientation of the nanostructures to design a metasurface with three working modes.”

The researchers describe the new device in Optics Express. They also showed that depending on the light used, the metasurface would generate a holographic image or a structural-color nanoprinting image with or without polarization-dependent watermarks.

“Our tiny metasurface could be easily attached to currency, ID cards, credit cards, certificates, watches or rings for anticounterfeiting,” said Dai. “Because this multi-functional metasurface features twofold safeguards, it could provide a simple but effective approach to fight against counterfeiting.”

A three-in-one device

Although other metasurface-based anticounterfeiting devices have been developed, the hidden information is usually

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