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Optical Engineering

Power scaling of quantum cascade lasers via multiemitter beam combining
Author(s): Stefan Hugger; Rolf Aidam; Wolfgang Bronner; Frank Fuchs; Rainer Lösch; Quankui K. Yang; Joachim Wagner; Eugen Romasew; Michael Raab; Hans-Dieter Tholl; Bernd Höfer; André L. Matthes
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Paper Abstract

Different approaches to power scaling of 4.5- to 5-µm emitting quantum cascade (QC) lasers by multiemitter beam combining are investigated. Spectral beam combining of linear arrays of QC lasers consisting of several individual emitters located side by side is demonstrated as a first variant, using an external cavity equipped with a diffraction grating and a partially transmitting output mirror providing wavelength-selective feedback to each emitter. In this way, spectral beam combining of up to eight individual QC lasers is achieved with an optical coupling efficiency of 60% for an array of six emitters. The resulting beam quality (M2 < 2 for both fast and slow axes) is close to that observed for single emitters. As a second approach, a linear array of QC lasers is coupled to a custom-made array of silicon microlenses positioned in front of the output facets of the QC lasers. This technique produces a set of closely spaced parallel output beams, strongly overlapping in the far field, without introducing any coupling losses. The resulting beam divergence is given by the aperture size of the microlenses, which is limited by the center-to-center spacing of the QC lasers (500 µm in our case).

Paper Details

Date Published: 1 November 2010
PDF: 5 pages
Opt. Eng. 49(11) 111111 doi: 10.1117/1.3498766
Published in: Optical Engineering Volume 49, Issue 11
Show Author Affiliations
Stefan Hugger, Fraunhofer-Institut für Angewandte Festkörperphysik (Germany)
Rolf Aidam, Fraunhofer-Institut für Angewandte Festkörperphysik (Germany)
Wolfgang Bronner, Fraunhofer-Institut für Angewandte Festkörperphysik (Germany)
Frank Fuchs, Fraunhofer-Institut für Angewandte Festkörperphysik (Germany)
Rainer Lösch, Fraunhofer-Institut für Angewandte Festkörperphysik (Germany)
Quankui K. Yang, Fraunhofer-Institut für Angewandte Festkörperphysik (Germany)
Joachim Wagner, Fraunhofer-Institut für Angewandte Festkörperphysik (Germany)
Eugen Romasew, Diehl BGT Defence GmbH & Co. KG (Germany)
Michael Raab, Diehl BGT Defence GmbH & Co. KG (Germany)
Hans-Dieter Tholl, Diehl BGT Defence GmbH & Co. KG (Germany)
Bernd Höfer, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
André L. Matthes, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)

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