17 February 2010 Development of asymmetric epitaxial structures for 65% efficiency laser diodes in the 9xx-nm range
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High-power single emitters have recently become a viable alternative to laser diode bars for fiber pumping applications. Single emitters offer a tenfold increase in brightness over bars, and can be optically combined to scale the power towards 100 W with high brightness. Wall-plug efficiencies >60% are needed to warrant the use of fiber-coupled single emitters in fiber laser systems, which requires careful minimization of the optical loss, electrical resistance and operating voltage of the emitters. Epitaxial wafer design necessarily involves multiple trade-offs, since doping concentrations have opposing effects on the electrical resistance and optical losses. In this paper, we report asymmetric epitaxial waveguide designs for high-efficiency laser operation at 9xx nm. We present a simulation study of the influence of design parameters such as the number of quantum wells, doping profiles, and overlap integral of each epilayer. We also show that by introducing an auxiliary waveguide into the lower cladding, we can control the overlap of the optical mode with the doping profiles - as well as the vertical far-field - without compromising the electrical resistance. The optimized structures were grown and devices fabricated, with optical losses reduced to 0.5 cm-1, and resistivity to 6.5 Ohm×sq.cm. An optical power of 10 W with >60% efficiency was achieved from 100 μm stripe emitters.
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Moshe Levy, Moshe Levy, Yoram Karni, Yoram Karni, Noam Rapaport, Noam Rapaport, Yaroslav Don, Yaroslav Don, Yuri Berk, Yuri Berk, Dan Yanson, Dan Yanson, Shalom Cohen, Shalom Cohen, Jacob Oppenheim, Jacob Oppenheim, "Development of asymmetric epitaxial structures for 65% efficiency laser diodes in the 9xx-nm range", Proc. SPIE 7583, High-Power Diode Laser Technology and Applications VIII, 75830J (17 February 2010); doi: 10.1117/12.843661; https://doi.org/10.1117/12.843661

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