Dr. Andreas Grohe Profile

Dr. Andreas Grohe

at II-VI DirectPhotonics

SPIE Involvement:

Author

Proceedings Article | 22 February 2017 Presentation + Paper

Diode lasers for direct application by utilizing a trepanning optic for remote oscillation welding of aluminum and copper

Haro Fritsche, Norbert Müller, Fabio Ferrario, Sebastian Fetissow, Andreas Grohe, Thomas Hagen, Ronny Steger, Tristan Katzemaikat, David Ashkenasi, Wolfgang Gries

Proceedings Volume 10097, 100970N (2017) https://doi.org/10.1117/12.2253007

KEYWORDS: Aluminum, Semiconductor lasers, Copper, Collimation, Continuous wave operation, Laser systems engineering, Free space optics, Fiber coupled lasers, Free space, Materials processing

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We report the first direct diode laser module integrated with a trepanning optic for remote oscillation welding. The trepanning optic is assembled with a collimated DirectProcess 900 laser engine. This modular laser is based on single emitters and beam combiners to achieve fiber coupled modules with a beam parameter product or BPP < 8 mm mrad at all power levels up to 1 kW, as well as free space collimated outputs with even lower BPP. The initial design consists in vertically stacking several diodes in the fast axis which leads to a rectangular output of about 100 W with BPP of <3.5 mm*mrad in the fast axis and <5 mm*mrad in the slow axis. Next, further power scaling is accomplished by polarization combining and wavelength multiplexing yielding high optical efficiencies of more than 80% and resulting in a building block module with over 500 W launched into a 100 μm fiber with 0.15 NA. The beam profile of the free space module remains rectangular, with a nearly flat top and conserves the beam parameter product of the original vertical stack without the power loss of fiber coupling. The 500 W building blocks feature a highly flexible emitting wavelength bandwidth. New wavelengths can be configured by simply exchanging parts and without modifying the production process. This design principle provides the option to adapt the wavelength configuration to match a broad set of applications, from the UV to the visible and to the far IR depending on the commercial availability of laser diodes. This opens numerous additional applications like laser pumping, scientific and medical applications, as well as materials processing applications such as cutting and welding of copper aluminum or steel. Furthermore, the module’s short lead lengths enable very short pulses. Integrated with electronics, the module’s pulse width can be adjusted from micro-seconds to cw mode operation by simple software commands. An optical setup can be directly attached instead of a fiber to the laser module thanks to its modular design. This paper’s experimental results are based on a trepanning optic attached to the laser module. Alltogether the setup approximately fits in a shoe box and weighs less than 20 kg which allows for direct mounting onto a 3D-gantry system. The oscillating weld performance of the 500 W direct diode laser utilizing a novel trepanning optic is discussed for its application to aluminum/aluminum and aluminum/copper joints.

Proceedings Article | 16 March 2016 Paper

Comparative study of broadband, narrowband and multi-wavelength resonant pumping of Er:YAG lasers

H. Fritsche, O. Lux, M. Gaertner, A. Grohe, W. Gries, H. J. Eichler

Proceedings Volume 9726, 972606 (2016) https://doi.org/10.1117/12.2213321

KEYWORDS: Er:YAG lasers, Semiconductor lasers, Diodes, Absorption, Laser systems engineering, Methane, Multiplexing, Laser crystals, Crystals, Solid state lasers

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Proceedings Article | 4 March 2016 Paper

Building block diode laser concept for high brightness laser output in the kW range and its applications

Fabio Ferrario, Haro Fritsche, Andreas Grohe, Thomas Hagen, Holger Kern, Ralf Koch, Bastian Kruschke, Axel Reich, Dennis Sanftleben, Ronny Steger, Till Wallendorf, Wolfgang Gries

Proceedings Volume 9733, 97330G (2016) https://doi.org/10.1117/12.2214067

KEYWORDS: Buildings, Semiconductor lasers, High power lasers, Collimation, Diodes, Electronics, Laser applications, Lenses, Polarization, Multiplexing, Laser cutting, Fiber lasers, Laser systems engineering, Control systems, Optical filters, Laser development

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The modular concept of DirectPhotonics laser systems is a big advantage regarding its manufacturability, serviceability as well as reproducibility. By sticking to identical base components an economic production allows to serve as many applications as possible while keeping the product variations minimal. The modular laser design is based on single emitters and various combining technics.

In a first step we accept a reduction of the very high brightness of the single emitters by vertical stacking several diodes in fast axis. This can be theoretically done until the combined fast axis beam quality is on a comparable level as the individual diodes slow axis beam quality without loosing overall beam performance after fiber coupling. Those stacked individual emitters can be wavelength stabilized by an external resonator, providing the very same feedback to each of those laser diodes which leads to an output power of about 100 W with BPP of <3.5 mm*mrad (FA) and <5 mm*mrad (SA). In the next steps, further power scaling is accomplished by polarization and wavelength multiplexing yielding high optical efficiencies of more than 80% and resulting in a building block module with about 500 W launched into a 100 μm fiber with 0.15 NA. Higher power levels can be achieved by stacking those building blocks using the very same dense spectral combing technique up to multi kW Systems without further reduction of the BPP.

The 500 W building blocks are consequently designed in a way that they feature a high flexibility with regard to their emitting wavelength bandwidth. Therefore, new wavelengths can be implemented by only exchanging parts and without any additional change of the production process. This design principal theoretically offers the option to adapt the wavelength of those blocks to any applications, from UV, visible into the far IR as long as there are any diodes commercially available. This opens numerous additional applications like laser pumping, scientific applications, materials processing such as cutting and welding of copper aluminum or steel and also medical application.

Typical operating at wavelengths in the 9XX nm range, these systems are designed for and mainly used in cutting and welding applications, but adapted wavelength ranges such as 793 nm and 1530 nm are also offered. Around 15XX nm the diodes are already successfully used for resonant pumping of Erbium lasers [1].

Furthermore, the fully integrated electronic concept allows addressing further applications, as due to short lead lengths it is capable of generating very short μs pulses up to cw mode operation by simple software commands.

Proceedings Article | 1 April 2015 Paper

Highly modular high-brightness diode laser system design for a wide application range

Haro Fritsche, Bastian Kruschke, Ralf Koch, Fabio Ferrario, Holger Kern, Ullrich Pahl, Einar Ehm, Silke Pflueger, Andreas Grohe, Wolfgang Gries

Proceedings Volume 9348, 93480A (2015) https://doi.org/10.1117/12.2080123

KEYWORDS: Semiconductor lasers, Diodes, Laser systems engineering, Laser development, Collimation, Materials processing, Fiber couplers, Resonators, Polarization, Laser cutting

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Proceedings Article | 1 April 2015 Paper

Beam combining techniques for high-power high-brightness diode lasers

Bastian Kruschke, Haro Fritsche, Holger Kern, Thomas Hagen, Ulrich Pahl, Ralf Koch, Andreas Grohe, Wolfgang Gries

Proceedings Volume 9346, 934614 (2015) https://doi.org/10.1117/12.2079553

KEYWORDS: Diodes, Semiconductor lasers, Polarization, Collimation, Optical filters, Multiplexing, Reliability, High power lasers, Laser systems engineering, Fiber Bragg gratings

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Proceedings Article | 26 March 2015 Paper

Multi-wavelength resonant pumping of Er:YAG lasers for energy efficient trace gas detection systems

Haro Fritsche, Oliver Lux, Casey Schuett, Martin Gaertner, Ronny Juhre, Andreas Grohe, Wolfgang Gries, Hans Eichler

Proceedings Volume 9342, 93420C (2015) https://doi.org/10.1117/12.2080232

KEYWORDS: Er:YAG lasers, Semiconductor lasers, Absorption, Methane, Laser systems engineering, Laser applications, Laser damage threshold, LIDAR, Diodes, Laser resonators

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Proceedings Article | 9 March 2015 Paper

Direct diode lasers and their advantages for materials processing and other applications

Haro Fritsche, Fabio Ferrario, Ralf Koch, Bastian Kruschke, Ulrich Pahl, Silke Pflueger, Andreas Grohe, Wolfgang Gries, Florian Eibl, Stefanie Kohl, Michael Dobler

Proceedings Volume 9356, 93560I (2015) https://doi.org/10.1117/12.2080208

KEYWORDS: Semiconductor lasers, Laser cutting, Laser systems engineering, Materials processing, Diodes, Laser applications, Modulation, Absorption, Solid state lasers, Fiber lasers

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The brightness of diode lasers is improving continuously and has recently started to approach the level of some solid state lasers. The main technology drivers over the last decade were improvements of the diode laser output power and divergence, enhanced optical stacking techniques and system design, and most recently dense spectral combining. Power densities at the work piece exceed 1 MW/cm² with commercially available industrial focus optics. These power densities are sufficient for cutting and welding as well as ablation. Single emitter based diode laser systems further offer the advantage of fast current modulation due their lower drive current compared to diode bars. Direct diode lasers may not be able to compete with other technologies as fiber or CO₂-lasers in terms of maximum power or beam quality. But diode lasers offer a range of features that are not possible to implement in a classical laser. We present an overview of those features that will make the direct diode laser a very valuable addition in the near future, especially for the materials processing market. As the brightness of diode lasers is constantly improving, BPP of less than 5mm*mrad have been reported with multikW output power. Especially single emitter-based diode lasers further offer the advantage of very fast current modulation due to their low drive current and therefore low drive voltage. State of the art diode drivers are already demonstrated with pulse durations of <10μs and repetition rates can be adjusted continuously from several kHz up to cw mode while addressing power levels from 0-100%. By combining trigger signals with analog modulations nearly any kind of pulse form can be realized. Diode lasers also offer a wide, adaptable range of wavelengths, and wavelength stabilization. We report a line width of less than 0.1nm while the wavelength stability is in the range of MHz which is comparable to solid state lasers. In terms of applications, especially our (broad) wavelength combining technology for power scaling opens the window to new processes of cutting or welding and process control. Fast power modulation through direct current control allows pulses of several microseconds with hundreds of watts average power. Spot sizes of less than 100 μm are obtained at the work piece. Such a diode system allows materials processing with a pulse parameter range that is hardly addressed by any other laser system. High productivity material ablation with cost effective lasers is enabled. The wide variety of wavelengths, high brightness, fast power modulation and high efficiency of diode lasers results in a strong pull of existing markets, but also spurs the development of a wide variety of new applications.

Proceedings Article | 2 May 2014 Paper

Generating a high brightness multi-kilowatt laser by dense spectral combination of VBG stabilized single emitter laser diodes

H. Fritsche, Ralf Koch, B. Krusche, F. Ferrario, Andreas Grohe, S. Pflueger, W. Gries

Proceedings Volume 9134, 91340U (2014) https://doi.org/10.1117/12.2052582

KEYWORDS: Semiconductor lasers, Diodes, Resonators, Reflectivity, Laser stabilization, Collimation, Polarization, Fiber Bragg gratings, Fiber couplers, High power lasers

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Proceedings Article | 25 February 2009 Paper

Novel laser technologies for crystalline silicon solar cell production

Andreas Grohe, Annerose Knorz, Jan Nekarda, Ulrich Jäger, Nicola Mingirulli, Ralf Preu

Proceedings Volume 7202, 72020P (2009) https://doi.org/10.1117/12.810128

KEYWORDS: Silicon, Solar cells, Semiconducting wafers, Etching, Laser drilling, Absorption, Semiconductor lasers, Laser processing, Laser ablation, Dielectrics

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Proceedings Article | 12 May 2006 Paper

Laser applications in crystalline silicon solar cell production

A. Grohe, R. Preu, S. Glunz, G. Willeke

Proceedings Volume 6197, 619717 (2006) https://doi.org/10.1117/12.663225

KEYWORDS: Solar cells, Semiconducting wafers, Silicon, Laser applications, Laser processing, Aluminum, Crystals, Dielectrics, Laser crystals, Silicon solar cells

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Showing 5 of 10 publications

Conference Committee Involvement (1)

Laser-based Micro- and Nanopackaging and Assembly IV

27 January 2010 | San Francisco, California, United States

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