7 March 2014 Simple design for fiber coupled 9xx nm kW-QCW pump module with high duty cycle based on customized chips and lateral heat removal
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Abstract
High power 9xxnm QCW- pump modules are very interesting for high- and ultra-high-energy laser systems. Main relevant issues beside price and power conversion efficiency are long term stability of the mounting scheme and stable fiber coupling. We present a design based on diode laser stacks with lateral heat removal. A single stack element consists of a diode laser, which is soldered on both sides to CuW carriers using AuSn. Life test over 1000 h showed no degradation. DCB coolers are subsequently soldered onto both outer sides of the stack. The thermal resistance of a single stack element is about 1.7 K/W. For >3 J pulse energy the stack contains 28 elements. ≥60% power conversion efficiency of the used 940 nm diode laser chips at 120 W output power allows ≥20% duty cycle without substantial heating (maximum measured output power >200 W). The light is collimated in vertical direction for each stack element. We choose a size for the FAC which allows staggering the beams of two stacks. The diode laser chips have an aperture width of 1.2 mm and a lateral divergence <14° (95 % power) at 120 W. Fiber coupling is performed by cylindrical lenses in both directions. For 6 J pump energy two stacks are used, coupled into 1.9 mm diameter fiber with a high optical coupling efficiency of >90 %. The principle design is very flexible to match other demands in fiber size and output power.
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Wolfgang Pittroff, Bernd Eppich, Götz Erbert, René Platz, Dieter Tyralla, Günther Traenkle, "Simple design for fiber coupled 9xx nm kW-QCW pump module with high duty cycle based on customized chips and lateral heat removal", Proc. SPIE 8965, High-Power Diode Laser Technology and Applications XII, 896515 (7 March 2014); doi: 10.1117/12.2036949; https://doi.org/10.1117/12.2036949
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