Narrow-Stripe Broad-Area Lasers With Distributed-Feedback Surface Gratings as Brilliant Sources for High Power Spectral Beam Combining Systems
J. Decker , P. Crump, J. Fricke, H. Wenzel, A. Maaßdorf, G. Erbert, and G. Tränkle
Published in:
Proc. SPIE, vol. 8965, Photonics West, San Francisco, USA, Feb. 1-6, 89650I (2014).
Abstract:
Laser systems based on spectral beam combining (SBC) of broad-area (BA) diode lasers are promising tools for material processing applications. However, the system brightness is limited by the in-plane beam parameter product, BPP, of the BA lasers, which operate with a BPP of > 3mm-mrad. The EU project BRIDLE (www.bridle.eu) is developing novel diode laser sources for such systems, and several technological advances are sought. For increased system brightness and optimal fiber-coupling the diode lasers should operate with reduced BPP and vertical far eld angle (95% power content), ΘV95. The resulting diode lasers are fabricated as mini-bars for reduced assembly costs. Gratings are integrated into the mini-bar, with each laser stripe emitting at a different wavelength. In this way, each emitter can be directed into a single fibre via low-cost dielectric filters. Distributed-feedback narrow-stripe broad-area (DFB-NBA) lasers are promising candidates for these SBC systems. We review here the design process and performance achieved, showing that DFB-NBA lasers with stripe width, W = 30 µm, successfully cut off higher-order lateral modes, improving BPP. Uniform, surface-etched, 80th-order Bragg gratings are used, with weak gratings essential for high efficiency. To date, such DFB-NBA sources operate with > 50% efficiency at output power, Pout > 6 W, with BPP < 1.8 m-mrad and ΘV95∼36°. The emission wavelength is about 970 nm and the spectral width is < 0.7 nm (95% power). The BPP is half that of a DFB-BA lasers with W = 90 µm. We conclude with a review of options for further performance improvements.
Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany
Keywords:
high power, high efficiency, narrow stripe, broad area lasers, distributed feedback, surface gratings.
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