Suppression of the Focal Shift of Single-Mode Laser with a Miniature Laser Processing Head

We propose a miniature processing head for laser cutting of metal sheets. The thermally-induced focal shift is exacerbated at low values of the beam parameter product, but it is possible to arrange the optical elements such that the focal shift and beam waist variation cancel out. Collimating and focusing low-NA beams with short focal lenses make it possible to use standard plano-convex lenses without causing appreciable spherical aberrations, but the higher power density calls for lowabsorption optics in order to mitigate thermal aberrations. The use of millimeter-size optics will pave the way to lighter processing heads, and this will enable an increased cutting speed in contours at a reduced electrical consumption. It can thus be considered as an alternative to remote cutting or to the addition of local axes to conventional gantry systems.