20 March 2008 High brightness fiber laser pump sources based on single emitters and multiple single emitters
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Driven by the potential of the fiber laser market, the development of high brightness pump sources has been pushed during the last years. The main approaches to reach the targets of this market had been the direct coupling of single emitters (SE) on the one hand and the beam shaping of bars and stacks on the other hand, which often causes higher cost per watt. Meanwhile the power of single emitters with 100μm emitter size for direct coupling increased dramatically, which also pushed a new generation of wide stripe emitters or multi emitters (ME) of up to 1000μm emitter size respectively "minibars" with apertures of 3 to 5mm. The advantage of this emitter type compared to traditional bars is it's scalability to power levels of 40W to 60W combined with a small aperture which gives advantages when coupling into a fiber. We show concepts using this multiple single emitters for fiber coupled systems of 25W up to 40W out of a 100μm fiber NA 0.22 with a reasonable optical efficiency. Taking into account a further efficiency optimization and an increase in power of these devices in the near future, the EUR/W ratio pushed by the fiber laser manufacturer will further decrease. Results will be shown as well for higher power pump sources. Additional state of the art tapered fiber bundles for photonic crystal fibers are used to combine 7 (19) pump sources to output powers of 100W (370W) out of a 130μm (250μm) fiber NA 0.6 with nominal 20W per port. Improving those TFB's in the near future and utilizing 40W per pump leg, an output power of even 750W out of 250μm fiber NA 0.6 will be possible. Combined Counter- and Co-Propagated pumping of the fiber will then lead to the first 1kW fiber laser oscillator.
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Torsten Scheller, Torsten Scheller, Lars Wagner, Lars Wagner, Jürgen Wolf, Jürgen Wolf, Guido Bonati, Guido Bonati, Falk Dörfel, Falk Dörfel, Thomas Gabler, Thomas Gabler, } "High brightness fiber laser pump sources based on single emitters and multiple single emitters", Proc. SPIE 6876, High-Power Diode Laser Technology and Applications VI, 68760Z (20 March 2008); doi: 10.1117/12.761554; https://doi.org/10.1117/12.761554

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