Dynamics of actively mode-locked Quantum Cascade Lasers

The impact of upper state lifetime and spatial hole burning on pulse shape and stability in actively mode locked QCLs is investigated by numerical simulations. It is shown that an extended upper state lifetime is necessary to achieve stable isolated pulse formation per roundtrip. Spatial hole burnin...

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Bibliographic Details
Published in:Optics express 2010-06, Vol.18 (13), p.13616-13630
Main Authors: Gkortsas, V-M, Wang, C, Kuznetsova, L, Diehl, L, Gordon, A, Jirauschek, C, Belkin, M A, Belyanin, A, Capasso, F, Kärtner, F X
Format: Article
Language:English
Subjects:
Computer Simulation
Equipment Design
Infrared Rays
Lasers, Semiconductor
Models, Theoretical
Optics and Photonics - instrumentation
Optics and Photonics - methods
Semiconductors
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Summary:The impact of upper state lifetime and spatial hole burning on pulse shape and stability in actively mode locked QCLs is investigated by numerical simulations. It is shown that an extended upper state lifetime is necessary to achieve stable isolated pulse formation per roundtrip. Spatial hole burning helps to reduce the pulse duration by supporting broadband multimode lasing, but introduces pulse instabilities which eventually lead to strongly structured pulse shapes that further degrade with increased pumping. At high pumping levels gain saturation and recovery between pulses leads to suppression of mode locking. In the absence of spatial hole burning the laser approaches single-mode lasing, while in the presence of spatial hole burning the mode locking becomes unstable and the laser dynamics does not reach a steady state anymore.
ISSN:1094-4087
1094-4087
DOI:10.1364/OE.18.013616