Advanced high-power laser diode combination design for laser scanning applications

Laser cutters and engraving devices traditionally feature a high-power CO2 laser in combination with a scanning unit. However, within the laser processing industry, a growing interest arose in the use and combination of laser diode sources, enabling a more compact design featuring a longer estimated lifespan. Therefore, we investigate and compare different laser diode combination configurations, while evaluating their applicability in a compact laser scanning configuration. Specifically, as a case study, we target the combination of 4 high-power laser diodes, pursuing a collimated, homogenous and symmetrical output beam, while minimizing light losses. An optimal laser diode combination design was achieved by use of aspherical lenses, knife-edge mirrors and a polarizing beam splitter. Two laser diodes are oriented to emit p-polarized light, while the other emit s-polarized light. In front of each laser diode, an aspherical lens is mounted to collect and collimate the laser beam. The two collimated s-polarized laser beams and the two p-polarized beams are each combined using a knife-edge mirror, after which the s- and p-polarized beam are combined by a polarizing beam splitter, giving rise to a single collimated output beam that can be used as input for the scanning unit. Following the optimization and tolerancing of the design, the laser diode combination system was successfully demonstrated in a proof-of-principle laboratory configuration indicating a homogeneous and collimated illumination beam at the entrance of the scan head, paving the way towards the integration and combination of multiple laser diode sources for use in high-power laser cutting and marking applications.