Efficient High-Power Laser Diodes

• Published in: IEEE journal of selected topics in quantum electronics Vol. 19; no. 4; p. 1501211
• Main Authors: Crump, Paul, Erbert, Gotz, Wenzel, Hans, Frevert, Carlo, Schultz, Christoph M., Hasler, Karl-Heinz, Staske, Ralf, Sumpf, Bernd, Maassdorf, Andre, Bugge, Frank, Knigge, Steffen, Trankle, Gunther
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.07.2013; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Current measurement; Diodes; Efficiency; Optical losses; Optical waveguides; Power conversion; quantum-well lasers; Resistance; Threshold current; Voltage measurement
• ISSN: 1077-260X; 1558-4542
• DOI: 10.1109/JSTQE.2013.2239961

High-power broad-area diode lasers are the most efficient light sources, with 90-μm stripe GaAs-based 940-980 nm single emitters delivering > 10 W optical output at a power conversion efficiency η E (10 W) > 65%. A review of efforts to increase η E is presented here and we show that for well-optimized structures, the residual losses are dominated by the p -side waveguide and nonideal internal quantum efficiency η i . The challenge in measuring efficiency to sufficient precision is also discussed. We show that η E can most directly be improved using low heat sink temperature T HS with η E (10 W) reaching > 70% at T HS = -50 °C. In contrast, increases in η E at T HS = 25 °C require improvements in both material quality and design, with growth studies targeting increased η i and reduced threshold current and design studies seeking to mitigate the impact of the p -side waveguide. "Extreme, double asymmetric" (EDAS) designs are shown to substantially reduce p -side losses, at the penalty of increased threshold current. The benefit of EDAS designs is shown here using diode lasers with 30-μm stripes, (in development as high beam quality sources for material processing). Efficiency increases of ~ 10% relative to conventional designs are demonstrated at high powers.