Metal Colorization Using Picosecond Laser Pulses

Abstract

In the last few decades, the nanoscale fabrication of metallic structures has demonstrated promising applications in security (e.g. cryptography), photochemistry (e.g. plasmonassisted photo-chemistry), decoration (e.g. colouring), biocompatibility of implants and more. To fabricate such subwavelength nanostructures, we typically resort to the use of several nanolithography techniques that are lengthy and incompatible with large-scale production on complex substrates. For this purpose, we invented an innovative technique for the fast fabrication of nanostructures via the use of a picosecond laser. We used this technique to produce colourful coins for the Royal Canadian Mint which were presented at the World Money Fair in Germany in 2015 as a world rst. To ensure the long-term survival of these plasmonic colours, a new dual-layer passivation technique was conceived based on a atomic deposition process, to meet the commercialisation requirements of our industrial partner. A new burst colouring technology was also invented that allows for the creation of more visually appealing colours. These laser burst colours were also shown to have a high sensing potential and an overall better visual response to the application of the passivation layer.