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Contrôle cohérent des états électroniques d'une boîte quantique unique

Abstract : We have studied the coherence properties of one electron-pair state confined in a single quantum dot (QD). Two kinds of dots are studied: monolayer step-induced GaAs QDs and self-organized InAs QDs. In order to probe at resonance the excitonic intrinsic properties, the QDs are embedded in a one-dimensional waveguide. The QD luminescence is then collected from the top surface of the waveguide, so that we can separate photons coming from excitation and luminescence. Firstly, We demonstrate the existence of a strong coupling regime between a single QD and light pulses by observing Rabi oscillations of the micro-photoluminescence as a function of the pulse area. Secondly, the electron-hole pair can be driven by a pair of phase-tailored pulses in a coherent control experiment. Depending on the relative phase between the two pulses, constructive or destructive interferences can enhance or destroy the QD emission during the coherence time. Two interesting coupling regimes have been investigated. The case of an excitation with π-pulses allows to measure lifetimes, T1, of excited states, whereas π/2-pulses are used to measure the coherence time, T2, of the fundamental transition. The results show that the total decoherence time T2 (170 ps) is comparable to the effective exciton lifetime T1 (200 ps) although not reaching the upper theoretical limit of 2T1. We conclude that energy relaxation and pure dephasing processes due to virtual scattering with phonons contribute on an equal footing to the loss of coherence.
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https://tel.archives-ouvertes.fr/tel-00530599
Contributor : Alexandre Enderlin <>
Submitted on : Friday, October 29, 2010 - 2:22:37 PM
Last modification on : Wednesday, December 9, 2020 - 3:10:39 PM
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  • HAL Id : tel-00530599, version 1

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Alexandre Enderlin. Contrôle cohérent des états électroniques d'une boîte quantique unique. Matière Condensée [cond-mat]. Université Pierre et Marie Curie - Paris VI, 2010. Français. ⟨tel-00530599⟩

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