P. Crump, G. Erbert, H. Wenzel, C. Frevert, C.M. Schultz, K.-H. Hasler, R. Staske, B. Sumpf, A. Maaßdorf, F. Bugge, S. Knigge, and G. Tränkle

Published in:

IEEE J. Sel. Top. Quantum Electron., vol. 19, no. 4, pp. 1501211 (2013).

Abstract:

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(10W) > 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.

Index Terms:

Power conversion, quantum-well lasers.

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