4 March 2016 Multi-kW high-brightness fiber coupled diode laser based on two dimensional stacked tailored diode bars
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Abstract
The demand for high brightness fiber coupled diode laser devices in the multi kW power region is mainly driven by industrial applications for materials processing, like brazing, cladding and metal welding, which require a beam quality better than 30 mm x mrad and power levels above 3kW. Reliability, modularity, and cost effectiveness are key factors for success in the market.

We have developed a scalable and modular diode laser architecture that fulfills these requirements through use of a simple beam shaping concept based on two dimensional stacking of tailored diode bars mounted on specially designed, tap water cooled heat sinks. The base element of the concept is a tailored diode laser bar with an epitaxial and lateral structure designed such that the desired beam quality in slow-axis direction can be realized without using sophisticated beam shaping optics. The optical design concept is based on fast-axis collimator (FAC) and slow-axis collimator (SAC) lenses followed by only one additional focusing optic for efficient coupling into a 400 μm fiber with a numerical aperture (NA) of 0.12.

To fulfill the requirements of scalability and modularity, four tailored bars are populated on a reduced size, tap water cooled heat sink. The diodes on these building blocks are collimated simply via FAC and SAC. The building blocks can be stacked vertically resulting in a two-dimensional diode stack, which enables a compact design of the laser source with minimum beam path length. For a single wavelength, up to eight of these building blocks, implying a total of 32 tailored bars, can be stacked into a submodule, polarization multiplexed, and coupled into a 400 μm, 0.12NA fiber. Scalability into the multi kW region is realized by wavelength combining of replaceable submodules in the spectral range from 900 – 1100 nm. We present results of a laser source based on this architecture with an output power of more than 4 kW and a beam quality of 25 mm x mrad.
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Andreas Bayer, Andreas Bayer, Andreas Unger, Andreas Unger, Bernd Köhler, Bernd Köhler, Matthias Küster, Matthias Küster, Sascha Dürsch, Sascha Dürsch, Heiko Kissel, Heiko Kissel, David A. Irwin, David A. Irwin, Christian Bodem, Christian Bodem, Nora Plappert, Nora Plappert, Maik Kersten, Maik Kersten, Jens Biesenbach, Jens Biesenbach, "Multi-kW high-brightness fiber coupled diode laser based on two dimensional stacked tailored diode bars", Proc. SPIE 9733, High-Power Diode Laser Technology and Applications XIV, 97330A (4 March 2016); doi: 10.1117/12.2212695; https://doi.org/10.1117/12.2212695
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