Homogenising and shaping a high-power laser for industrial materials processing presents challenges in both design and fabrication, requiring trade-offs between diffraction and homogenisation, avoiding hotspots in the beam and using materials that can handle very high CW power loading.
The beamshaper must achieve the required beam dimensions at the process plane, while maintaining a sufficiently uniform intensity homogeneity over the beam profile. In order to use the beamshaper with beams of high average or peak power, the optic should avoid generating spurious foci or retro-foci, which can damage other optics or cause air breakdown. This can be achieved by using a concave Micro Lens Array (MLA). Most MLA fabrication processes are best suited to making convex MLAs, but a concave MLA can be manufactured using the PowerPhotonic freeform fabrication process.
The ultra-smooth surface of all PowerPhotonic optics, with its intrinsically low scatter and the high power handling of our UV-fused silica substrates make them ideal for very high power handling.
The profile of a concave lenslet of a concave microlens array based diffraction homogenizer, left, and right the rectangular profile in the process plane (2mm x 2mm burn card)