An external cavity lasing system, which operates at 2.4 μm and involves an InGaAsSb Fabry-Pérot gain chip, was developed and characterized. The system was set up in a Littrow configuration to achieve a tuning range of about 100 nm. Continuous, mode-hope free tuning was observed with variation of grating angle. The threshold current of the lasing chip varied from 86 mA down to 70 mA for lasing in Fabry-Pérot (FP) and external cavity (ECL) modes, respectively. A dependence of the threshold current on lasing wavelength was observed. The tuning range was found to depend on the semiconductor gain profile and also on the intensity of the optical feedback through the collimation-dispersion system. Drifting of the wavelength, as observed in intra cavity semiconductor lasers, was not observed for drive currents of up to 350 mA in regions close to the gain peak. Single mode ECL lasing could be sustained in this range at a significantly weaker optical feedback. Traces of FP lasing were, however, observed at currents in the range of 100-200 mA for wavelengths in the shoulder regions of the gain profile. In these cases, an increase of drive current resulted in mode hopping to multi-mode FP lasing. Our results confirm the competing nature of FP lasing with that of ECL mode of lasing. The onset of multi-mode FP lasing, and eventual hopping to these modes, can be correlated with the gain profile, drive current, and optical feedback.

Date Published: 4 February 2013
PDF: 7 pages
Proc. SPIE 8631, Quantum Sensing and Nanophotonic Devices X, 86311R (4 February 2013); doi: 10.1117/12.2005196

Published in SPIE Proceedings Vol. 8631:
Quantum Sensing and Nanophotonic Devices X
Manijeh Razeghi, Editor(s)