Time-Resolved Investigations of Electronic Transport Dynamics in Quantum Cascade Lasers Based on Diagonal Lasing Transition

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Time-Resolved Investigations of Electronic Transport Dynamics in Quantum Cascade Lasers Based on Diagonal Lasing Transition

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Title: Time-Resolved Investigations of Electronic Transport Dynamics in Quantum Cascade Lasers Based on Diagonal Lasing Transition
Author: Choi, Hyunyong; Diehl, Laurent; Wu, Zong-Kwei; Giovannini, Marcella; Faist, Jérôme; Capasso, Federico; Norris, Theodore B.

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Citation: Choi, Hyunyong, Laurent Diehl, Zong-Kwei Wu, Marcella Giovannini, Jerome Faist, Federico Capasso, Theodore B. Norris. 2009. Time-resolved investigations of electronic transport dynamics in quantum cascade lasers based on diagonal lasing transition. IEEE Journal of Quantum Electronics 45(4): 307-321.
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Abstract: In this study, the nature of electronic transport in
quantum cascade lasers (QCLs) has been extensively investigated
using an ultrafast time-resolved, degenerate, pump-probe optical
technique. Our investigations enable a comprehensive understanding
of the gain recovery dynamics in terms of a coupling
of the electronic transport to the oscillating intracavity laser
intensity. In QCLs that have a lasing transition diagonal in real
space, studies of the near-threshold reveal that the transport of
electrons changes bias region from phonon-limited relaxation
(tens of picoseconds) below threshold to photon-driven transport
via stimulated emission (a few picoseconds) above threshold. The
gain recovery dynamics in the photon-driven regime is compared
with conventional four-level lasers such as atomic, molecular, and
semiconductor interband lasers. The depopulation dynamics out
of the lower lasing state is explained using a tight-binding tunneling
model and phonon-limited relaxation. For the superlattice
relaxation, it is possible to explain the characteristic picosecond
transport via dielectric relaxation; Monte Carlo simulations with
a simple resistor model are developed, and the Esaki–Tsu model
is applied. Subpicosecond dynamics due to carrier heating in
the upper subband are isolated and appear to be at most about
10% of the gain compression compared with the contribution of
stimulated emission. Finally, the polarization anisotropy in the
active waveguide is experimentally shown to be negligible on our
pump-probe data, supporting our interpretation of data in terms
of gain recovery and transport.
Published Version: doi:10.1109/JQE.2009.2013091
Other Sources: http://seas.harvard.edu/capasso/publications/Choi_IEEE_JQE_45_307_2009.pdf
Terms of Use: This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAA
Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:3445985
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