The coloring and color enhancement of noble metals via multi-burst picosecond pulses

We report on the fast angle-independent coloring of noble metals. The use of multi-burst on noble metals is observed to increase color saturation, in the case of silver, by up to ~50% compared to a non-burst laser coloring process. We already showed that non-burst laser coloring is the result of nanoparticle re-deposition on the sample surface and the activation of surface plasmons. For burst, these nanoparticles accompanied by 3 types of laser induced periodic surface structures (LIPSS). Finite-difference time-domain (FDTD) simulations of the multi-burst surfaces identified the high-spatial frequency LIPSS (HSFL) to be responsible for enhanced selective absorption and thereby higher color saturation. We report, for the first time, the creation of a full color palette on the surface of gold. In addition, we show the passivation of the silver colored surfaces via the deposition of thin layers of aluminum oxide by atomic layer deposition (ALD). The thickness of the aluminum oxide is also demonstrated to tune the colors.