Metal processing

Femtosecond milling of metal gives high quality but limited throughput, because the most efficient fluence is hard to reach at high average power. MHz burst mode splits one high-energy pulse into sub-pulses, which restores the optimum fluence and raises removal efficiency by 18% on aluminum, 44.5% on copper and 37% on steel.

Stainless steel, copper, tantalum and Kovar have all been cut with the same femtosecond laser, in foils from 50 to 125 µm thick. Only the pulse energy and scan parameters change between them, and the cut edges stay smooth and burr-free with a minimal heat-affected zone.

Femtosecond pulses roughen the metal surface until it absorbs almost all incident light, which leaves a black mark of high contrast and strong resistance to environmental effects. A gentler thermal load does the opposite job: it grows a thin oxide layer, and the layer thickness sets the color, with no inks or chemical additives.

Femtosecond pulses near the ablation threshold cover a metal surface in laser-induced periodic surface structures (LIPSS). The texture changes how the surface behaves rather than its shape: light absorption rises, wetting and tribological performance shift, and bacterial adhesion drops. Coarser patterns can be combined with LIPSS into hierarchical textures.

Femtosecond lasers are the best choice for cutting nitinol stents. Their ultra-short pulses cut with very high precision, so the edges come out smooth, with almost no burr and only a small heat-affected zone. That matters for stents, whose fine geometry and exact dimensions have to work inside the body.