Metal processing

Metal draws heat away fast, so longer pulses melt the edge and leave burrs and a wide heat-affected zone. Femtosecond laser pulses remove material before the heat spreads: stents and thin parts are cut with smooth, burr-free edges, surfaces are textured to change their properties, and metals are marked black or in color without inks.

Material processing
Material processing Glass Metal Polymer Other materials
Metal

Metal milling in MHz burst mode

Femtosecond milling is limited by throughput. There is an optimal fluence at which material is removed most efficiently, but at high average power that fluence is hard to reach: raising the repetition rate far enough pushes the process into thermal accumulation, and quality degrades. MHz burst mode splits the high-energy pulse into sub-pulses, so the optimum fluence is reached without that penalty.

In a study by A. Žemaitis et al., a FemtoLux was used to optimize machining of aluminum, copper and stainless steel by milling 110 cavities in a single sample, varying the repetition rate and the number of pulses per burst. Against the best single-pulse result, MHz bursts raised removal efficiency and rate by 18% on aluminum, 44.5% on copper and 37% on steel, and surface roughness came out lower.

Efficiently laser milled aluminum Fresnel lens mold, diameter 35 mm: (a) optical photograph, (b) 3D height map and (c) 2D profile from the middle of the structure.

Efficiently laser milled aluminum Fresnel lens mold, diameter 35 mm: (a) optical photograph, (b) 3D height map and (c) 2D profile from the middle of the structure.

Courtesy of FTMC.

Results of processing various metal samples with MHz burst

MaterialRemoval efficiencyRemoval rateSurface roughnessNo. of pulses in burst
Aluminum7.0 µm3/µJ9.2 mm3/min1.7 µm10
Copper4.2 µm3/µJ5.6 mm3/min2 µm5
Steel3.9 µm3/µJ5.1 mm3/min1.7 µm10
MaterialRemoval efficiencyRemoval rateSurface roughnessNo. of pulses in burst
(a) Experimental setup; (b) optimization of removal efficiency and rate for metals by variation of pulse repetition rate and number of pulses per burst; (c) correlation between removal efficiency and surface roughness; (d) different operation modes: single-pulse and MHz burst mode with 3 pulses indicated in burst mode.

(a) Experimental setup; (b) optimization of removal efficiency and rate for metals by variation of pulse repetition rate and number of pulses per burst; (c) correlation between removal efficiency and surface roughness; (d) different operation modes: single-pulse and MHz burst mode with 3 pulses indicated in burst mode.

Courtesy of FTMC.

Publications

Ablation FemtoLux
The ultrafast burst laser ablation of metals: Speed and quality come together
A. Žemaitis, U. Gudauskytė, S. Steponavičiūtė, P. Gečys, and M. Gedvilas, Optics & Laser Technology 180, 111458 (2024). DOI: 10.1016/j.optlastec.2024.111458.

Similar applications

Perforated disc cut in stainless steel.
Cutting of various metals

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.
Black-marked QR codes and logos on medical tweezers.
Black/color marking of metals

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.
Nitinol textured with a square grid, each cell filled with LIPSS ripples.
Metal surface texturing

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.
Nitinol demo part cut with two strut patterns, with lettering marked on the solid band between them.
Nitinol stent cutting

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.
All applications