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Controlling the spectral properties of quantum light sources based on a quantum dot in a nanowire

Abstract : This work aims at controlling the spectral properties of the photons that are emitted by a semiconductor quantum dot (QD) embedded in a photonic nanowire antenna. First, we conduct a theoretical study which unveils a new decoherence mechanism in this system. We show that, even at cryogenic temperature, the thermal vibrations of the nanowire induce a large spectral broadening that prevents the emission of indistinguishable photons. We propose three designs that suppress this decoherence channel thanks to an engineering of the mechanical properties of the nanowire. Next we introduce a nanowire optical nanocavity which offers a large acceleration of spontaneous emission (predicted Purcell factor of 6.3) that is maintained over a 30-nm-wide operation bandwidth. We fabricate a GaAs nanocavity which embeds InAs self-assembled QDs. Single QD spectroscopy reveals a maximal acceleration of spontaneous emission by a factor as large as 5.6 and a first lens collection efficiency of 0.35. Finally, we propose a strategy to tune the emission wavelength of a QD embedded in a nanowire antenna. On-chip electrodes generate an electrostatic force that bends the nanowire. The resulting strain modulates the QD bandgap energy. We realize a first generation of devices and discus preliminary wavelength tuning measurements. Overall, these results open promising perspectives for photonic quantum technologies, in particular for the realisation of advanced sources of quantum light.
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https://tel.archives-ouvertes.fr/tel-03523109
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Submitted on : Wednesday, January 12, 2022 - 2:44:11 PM
Last modification on : Friday, March 25, 2022 - 9:43:01 AM
Long-term archiving on: : Wednesday, April 13, 2022 - 11:05:07 PM

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  • HAL Id : tel-03523109, version 1

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Saptarshi Kotal. Controlling the spectral properties of quantum light sources based on a quantum dot in a nanowire. Quantum Physics [quant-ph]. Université Grenoble Alpes [2020-..], 2021. English. ⟨NNT : 2021GRALY039⟩. ⟨tel-03523109⟩

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