Product Code: PIC06_Plenary_2

Holistic Development of High Power Laser Sources and Corresponding Applications
Authors:
Reinhart Poprawe, Fraunhofer ILT; Aachen Germany
Peter Loosen, Fraunhofer-Institute für Laser Technology; Aachen Germany
Wolfgang Schulz, Fraunhofer-Institute für Laser Technology; Aachen Germany
Presented at PICALO 2006

With the advent of high power diode lasers of lifetimes in excess of 10,000 hours at long term operational power levels in the range of 100W per diode bar, diode pumped concepts moved into their rightful role as next generation sources. The main reason for this trend is the combination of laser efficiencies in the range of 15 to 25% at powers of several kW with the well known and increasingly applied advantage of fiber coupling. A particularly promising perspective similar to electrical networks is provided by concepts of laser power networks distributing the optical energy on demand in the production environment, especially for large scale production. In this paper, existing high power solid state lasers and new concepts in various states of development are analyzed with respect to their maturity and applicability. As a result, a laser roadmap is derived, which couples the specific properties of several lasers with the corresponding application parameters, material properties, product groups and markets. Specifically, the properties of diode pumped rod lasers, disk lasers, end pumped slab (so called inno-slab) lasers and fiber lasers are displayed and compared. The rotationally symmetric concepts of rod, fiber and disk configurations differ basically only in their relation of length to diameter, with disk and fiber laser staking the extreme positions. On the other hand, the inno-slab laser is set up in Cartesian symmetry for the purpose of obtaining highly efficient cooling, leading to the possibility of operating at extremely large pumping intensity and high gain, coupled, however with a requisite hybrid stable/ unstable resonator. Inno-slab lasers therefore are particularly well suited for q-swtich applications with pulse lengths in a range down to only a few ns for direct materials procesessing or frequency conversion. The new lasers discussed in the paper allow addressing new application areas. Examples will be shown in the areas of precision metal polishing with short pulse lasers, economical and attractive laser cleaning of large surfaces, SHADOW-welding of micro components, high speed precision marking of glass, high precision laser forming (selective laser melting) and precision drilling. In the case of direct diode laser applications, direct planar waveguide coupling and single shot simultaneous processing shall be discussed.