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, vol. 8965, Photonics West, San Francisco, USA, Feb. 1-6, 896515 (2014).
© 2014 COPYRIGHT SPIE--The International Society for Optical Engineering. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the SPIE.
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.
a Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany
b Technische Hochschule Wildau, Bahnhofstraße, 15745 Wildau, Germany
High power diode lasers, QCW lasers, fiber coupling, diode laser bonding.