Laser cutting using ultrashort pulse lasers can create highly accurate cuts with exceptional quality and a very low amount of damage to the substrate material. The material is removed by scanning along the contour of the desired cut. By using fast galvanometer scanners it is possible to obtain accurate, flexible, and relatively fast cutting processes.
Typical advantages of ultrashort pulse laser cutting are the absence of a heat affected zone, melt, cracks and burrs. No mechanical forces are applied on the substrate, making this cutting method ideal for delicate materials or thin foils. This also makes it possible to machine very thin walls. The cut width needed to cut through a substrate can be as small as the focussed laser spot, typically 10–30 μm. For thicker substrates it can be needed to widen the cutting groove, but still considerably thinner cuts can be obtained compared to mechanical dicing for example. In most applications the thickness of the material to be cut is below 1 mm.
Hard and brittle materials like glass or ceramics can be cut without cracks or chipping. The image here shows an example of several holes and slits cut into 400 μm thick alumina.
Ultrashort pulse lasers are an ideal tool for cutting of composite materials. Due to the very low heat input, even composites with large differences in thermal properties can be machined. Cutting carbon fiber reinforced composites for example can be problematic due to the high melting temperature of the carbon fibers in combination with a high thermal conductivity. Heat can be easily transported into the composite material by the fibers, leading to damage of the more sensitive matrix over a large distance. The low thermal input of an ultrashort pulse laser process can avoid this effect and results in excellent cut qualities, as shown in the first example below. The following SEM images show more examples of cuts in composite or multi-layer materials.
If multiple repetitions of the scan pattern are used to cut through material, the slope of the cut surface can be controlled by altering the scan pattern between the repetitions. This SEM image shows such a sloped cut in a stainless steel foil.