Regensburg 2007 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 4: Semiconductor Laser I
HL 4.4: Vortrag
Montag, 26. März 2007, 11:30–11:45, H13
Measurements of the Linewidth Enhancement Factor of Distributed Feedback Quantum Cascade Lasers by the Self-Mixing Technique — •Jens von Staden1, Tobias Gensty1, Wolfgang Elsäßer1, Guido Giuliani2, and Christian Mann3 — 1Institut für Angewandte Physik, Technische Universität Darmstadt, Schloßgartenstraße 7, 64289 Darmstadt, Germany — 2Dipartimento di Elettronica, Laboratorio Elettroottica, Università di Pavia, Via Ferrata 1, Pavia I-27100, Italy — 3Fraunhofer-Institut für Angewandte Festkörperphysik (IAF), Tullastrasse 72, 79108 Freiburg, Germany
We present measurements of the linewidth enhancement (α) factor of a distributed feedback (DFB) quantum cascade laser (QCL), using the interferometric self-mixing technique. The vality of this method has been shown for interband semiconductor lasers and is now transferred to the mid infrared wavelength range. In our experiments we use the QCL also to detect the self-mixing waveform by measuring the voltage drop variations across the device. The obtained self-mixing signal can then be used to evaluate both, the linewidth as well as the α-factor. Theoretical considerations predict the linewidth of QCLs to be extremly small. Limited by the resolution of the improved experimental setup, a reduced upper limit for the linewidth can be given. Our investigations of the α-factor have revealed a strong dependence on the injection current. Therefore the underlying mechanisms are further investigated. Thus we present measurements of the influence of the temperature dependent misalignment of the DFB grating on the value of the α-factor.