Surface texturing with lasers for protection against copying

Thanks to the latest technological advances lasers can perhaps in the future be used in the fight against copying by providing products with a texture.

Everybody is aware of the colourful patterns on bank notes, identity cards and labels (figure on the left). These come as a result of nano-structuring that breaks down the light into various colours (diffraction). They are often produced by electron or ion bundling technology. However, this technology is slow.

When treating a metal with laser pulses, it is known that structures are created (LIPSS - 'laser induced periodic surface structures'), which can also diffract light (figure at the centre). By controlling polarisation and time intervals between pulses, it has recently been possible to achieve 2D surface structures with a more uniform colour pattern (figure on the right).

This brings laser technology a step nearer towards being used against illegal copying.

Source

  • Fraggelakis F. Et al., Applied Surface Science 2019, nr. 470, p. 677-686