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Proceedings Paper

Emitter resolved analysis of packaged laser bars
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Paper Abstract

Thermo-mechanical stress occurring during the packaging process and during operation limits the reliability of high-power diode laser bars. The stress is caused by the mismatch of the thermal expansion coefficients between the heat sink and laser bar material. A soft solder layer can partially reduce the stress by relaxation. A convenient approach for reducing the stress is the matching of the thermal expansion of the heat sink to the laser bar material. The disadvantage of most expansion-matched heat sinks is a higher thermal resistance so that the device temperature increases and the lifetime decreases. For the development of thermal and strain optimized diode laser packages an analysis of both the thermal and strain distribution is reasonable. In this work the strain is analyzed by electroluminescence using the correlation between stress and the polarization properties of the laser bar radiation. This method allows a qualitative emitter resolved strain mapping along the slow-axis. Because of the correlation between temperature and wavelength a thermal analysis of mounted laser bars can be done by an emitter resolved spectral mapping. Irregularities in the thermal contact between laser bar and heat sink such as defects in the solder layer become visible by irregular emitter spectra. The work shows examples for the optimization of the package. The analysis of the thermal and strain distribution shows the advantages and disadvantages of the particular approaches, like variations of solder thickness or expansion matched packages.

Paper Details

Date Published: 13 February 2008
PDF: 10 pages
Proc. SPIE 6876, High-Power Diode Laser Technology and Applications VI, 68760O (13 February 2008); doi: 10.1117/12.764576
Show Author Affiliations
Thomas Westphalen, Fraunhofer Institute for Laser Technology (Germany)
Michael Leers, Fraunhofer Institute for Laser Technology (Germany)
Christian Scholz, Fraunhofer Institute for Laser Technology (Germany)
Konstantin Boucke, Fraunhofer Institute for Laser Technology (Germany)

Published in SPIE Proceedings Vol. 6876:
High-Power Diode Laser Technology and Applications VI
Mark S. Zediker, Editor(s)

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