Suppression of Higher-Order Lateral Modes in Broad-Area Diode Lasers by Resonant Anti-Guiding

H. Wenzel, P. Crump, J. Fricke, P. Ressel, and G. Erbert

Published in:

IEEE J. Quantum Electron., vol. 49, no. 12, pp. 1102-1108 (2013).

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For a maximum fiber-coupled power, high power broad-area diode lasers must operate with a small lateral far-field divergence at high continuous wave (CW) powers. However, these structures are laterally multi-moded, with a low beam quality and wide emission angles. We present a new approach to suppress higher-order lateral modes based on an anti-guiding layer with a high refractive index inserted at the edges of the active stripe. Simulations of planar waveguides containing germanium layers reveal that strong mode-coupling effects occur. These are found to vary as a function of the thickness of the inserted layer. By embedding the germanium layer in the outer region of a ridgewaveguide, the mode coupling effects result in a reduction of the modal gain of higher-order lateral modes. The lateral far-field divergence of fabricated 90-µm stripe lasers emitting at 980 nm and containing such an anti-guiding layer is narrowed by 3° at a CW output power of 10 W.

Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, D-12489 Berlin, Germany<

Index Terms:

Laser modes, semiconductor lasers, simulation.