Heading to 1 kW levels with laser bars of high-efficiency and emission wavelength around 880 nm and 940 nm

A. Pietrzak; M. Woelz; Ralf Huelsewede; Martin Zorn; Olaf Hirsekorn; J. Meusel; A. Kindsvater; Matthias Schroeder; V. Bluemel; J. Sebastian

doi:10.1117/12.2078642

13 March 2015 Heading to 1 kW levels with laser bars of high-efficiency and emission wavelength around 880 nm and 940 nm

A. Pietrzak, M. Woelz, Ralf Huelsewede, Martin Zorn, Olaf Hirsekorn, J. Meusel, A. Kindsvater, Matthias Schroeder, V. Bluemel, J. Sebastian

Author Affiliations +

Proceedings Volume 9348, High-Power Diode Laser Technology and Applications XIII; 93480E (2015) https://doi.org/10.1117/12.2078642
Event: SPIE LASE, 2015, San Francisco, California, United States

Abstract

High-power quasi-CW laser bars are of great interest as pump sources of solid-state lasers generating high-energy ultrashort pulses for high energy projects. These applications require a continuous improvement of the laser diodes for reliable optical output powers and simultaneously high electrical-to-optical power efficiencies. An overview is presented of recent progress at JENOPTIK in the development of commercial quasi-CW laser bars emitting around 880 nm and 940 nm optimized for peak performance. At first, performances of 1.5 mm long laser bars with 75% fill-factor are presented. Both, 880 nm and 940 nm laser bars deliver reliable power of 500 W with wall-plug-efficiencies (WPE) <55% within narrow beam divergence angles of 11° and 45° in slow-axis and fast-axis directions, respectively. The reliability tests at 500 W powers under application quasi- CW conditions are ongoing. Moreover, laser bars emitting at 880 nm tested under 100 μs current pulse duration deliver 1 kW output power at 0.9 kA with only a small degradation of the slope efficiency. The applications of 940 nm laser bars require longer optical pulses and higher repetition rates (1-2 ms, ~10 Hz). In order to achieve output powers at the level of 1 kW under such long pulse duration, heating of the laser active region has to be minimized. Power-voltage-current characteristics of 4 mm long cavity bars with 50% fill-factor based on an optimized laser structure for strong carrier confinement and low resistivity were measured. We report an output power of 0.8 kW at 0.8 A with <60% conversion efficiency (52% WPE). By increasing the fill-factor of the bars a further improvement of the WPE at high currents is expected.

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A. Pietrzak, M. Woelz, Ralf Huelsewede, Martin Zorn, Olaf Hirsekorn, J. Meusel, A. Kindsvater, Matthias Schroeder, V. Bluemel, and J. Sebastian "Heading to 1 kW levels with laser bars of high-efficiency and emission wavelength around 880 nm and 940 nm", Proc. SPIE 9348, High-Power Diode Laser Technology and Applications XIII, 93480E (13 March 2015); https://doi.org/10.1117/12.2078642

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