Researchers at Heriot-Watt University, in Edinburgh, have developed a tamper-proof hologram technology to replace serial numbers and barcodes that could help reduce trade in counterfeit goods.

Manufacturers of high-value goods such as electronics and aviation parts etch serial numbers into products, use bar codes or place polymer holographic stickers on items to provide identification and traceability of products and to assure customers of authenticity and quality. However, serial numbers and bar codes can be damaged, and stickers are vulnerable to tampering and counterfeiting.

Now, a team led by Duncan Hand, professor in the School of Engineering and Physical Sciences, is using an ultraviolet nanosecond-pulsed laser to sculpt unique holograms with micro-sized features directly onto the surface of metals. Individual laser pulses delivered at a rate of a few kHz melt the surface in a precise, localized way to produce optically smooth impressions on the metal. By manipulating the laser beam to create specific patterns, holographic structures are produced that can act as security markings for high-value products and components.

The holograms can generate diffractive images containing characters or logos as required. Image credit: Heriot-Watt University.The holograms can generate diffractive images containing characters or logos as required. Image credit: Heriot-Watt University.“The holograms are visible to the naked eye and appear as smooth, shiny textures," says Dr. Krystian Wlodarczyk, a researcher working on the project. "They’re robust to local damage and readable by using a collimated beam from a low-cost, commercially available laser pointer, so border agencies or consumers won’t need expensive technology to check an item’s authenticity. Actually, the holograms can also be read even using a flashlight from a smart phone.”

The holograms can generate diffractive images containing characters or logos as required via melting or a combination of melting and evaporation. The shape and geometry of the hologram pixels are important because they affect the optical performance of the holographic structure. To obtain the maximum efficiency (contrast) of the diffractive image produced by the hologram, the pixels must have a certain depth and ideally a flat, optically smooth base.

Having established that they can create the holograms on a variety of metals, the researchers are now investigating how to make them even smaller and whether they can be applied to other materials. Recent research has focused on adapting the process to create holograms on glass.

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