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Spectroscopie Optique de boîtes quantiques uniques: effets de l'environnement

Abstract : We have investigated the dephasing mechanisms in single self-organized InAs/GaAs quantum dots. First, an anti-Stokes photoluminescence signal (i. e. emission that occurs at energies higher than the excitation energy) was detected under continuous excitation. The study of this signal revealed the presence of a continuum of states lying between the wetting layer band-edge and the quantum dots levels. This continuum of states is coupled to the two-dimensional continuum of the wetting layer and also to the discrete states of the quantum dots. In fact it is of intrinsic origin and due to mixed transitions between discrete quantum dots and the two-dimensional continuum of states of the wetting layer. We have then studied the electronic excitations coherence properties by means of spectral linewidth measurements. In order to obtain a high enough spectral resolution, we have applied a Fourier Transform spectroscopy technique on the photoluminescence signal of a single quantum dot. A 0,5 microeV spectral resolution was obtained with this set-up. For excited transitions in quantum dots, we have shown that, instead of the predicted phonon bottleneck effect, the acoustic phonon induced dephasing is very efficient, with an efficiency greater than for InGaAs/GaAs quantum wells. This efficiency is basically due to the above-mentioned continuum of mixed-states. On the contrary, for the fundamental transition we have demonstrated the quenching of the acoustic phonon induced dephasing for quantum dots transitions energetically well-separated from this continuum of states. Finally, we have shown that a non-resonant excitation of the quantum dots increases the transition linewidths. A resonant excitation reduces the influence of the environment on the quantum dot decoherence. This indicates a way to reach the regime where the decoherence time is limited by the radiative lifetime.
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https://tel.archives-ouvertes.fr/tel-00002361
Contributor : Cécile Kammerer <>
Submitted on : Wednesday, February 5, 2003 - 12:23:04 PM
Last modification on : Monday, December 14, 2020 - 9:49:16 AM
Long-term archiving on: : Friday, April 2, 2010 - 8:04:39 PM

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  • HAL Id : tel-00002361, version 1

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Cécile Kammerer. Spectroscopie Optique de boîtes quantiques uniques: effets de l'environnement. Physique [physics]. Université Pierre et Marie Curie - Paris VI, 2002. Français. ⟨tel-00002361⟩

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