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Comparison between 50 W tapered laser arrays and tapered single emitters

: Scholz, C.; Boucke, K.; Poprawe, R.; Kelemen, M.T.; Weber, J.; Mikulla, M.; Weimann, G.


Zediker, M.S. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
High-power diode laser technology and applications IV : 23-25 January 2006, San Jose, California
Bellingham/Wash.: SPIE, 2006 (SPIE Proceedings Series 6104)
ISBN: 0-8194-6146-6
ISBN: 978-0-8194-6146-9
Paper 61040G
Conference "High-Power Diode Laser Technology and Applications" <2006, San Jose/Calif.>
Fraunhofer ILT ()

During the last few years high power diode laser arrays have become well established for direct material processing due to their high efficiency of more than 50%. But standard broad-area waveguide designs are susceptible to modal instabilities and filamentations resulting in low beam qualities. The beam quality increases by more than a factor of four by using tapered laser arrays, but so far they suffer from lower efficiencies. Therefore tapered lasers are mainly used today as single emitters in external resonator configurations. With increased output power and lifetime, they will be much more attractive for material processing and for pumping of fiber amplifiers. High efficiency tapered mini bars emitting at a wavelength of 980 nm are developed, and in order to qualify the bars, the characteristics of single emitters and mini bars from the same wafer have been compared. The mini bars have a width of 6 mm with 12 emitters. The ridge waveguide tapered lasers consist of a 500 µm long ridge and a 2000 µm long tapered section. The results show very similar behavior of the electro-optical characteristics and the beam quality for single emitters and bars. Due to different junction temperatures, different slope efficiencies were measured: 0.8 W/A for passively cooled mini bars and 1.0 W/A for actively cooled mini-bars and single emitters. The threshold current of 0.7 A per emitter is the same for single emitters and emitter arrays. Output powers of more than 50 W in continuous wave mode for a mini bar with standard packaging demonstrates the increased power of tapered laser bars.