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Romain Fons

Optical properties of semiconductor quantum dots embedded in photonic wire antennas

Published on 16 December 2020
Thesis presented December 16, 2020

A photonic wire antenna shapes the emission of a quantum dot (QD) into a directional beam, which can be efficiently collected by free-space optics. These photonic structures find applications in the emission of non-classical states of light (single photons, entangled pairs of photons) or in the generation of giant non-linearities, at the level of a single photon. This thesis contributes to a better understanding of the optical properties of InAs QDs integrated in photonic wire antennas through two main results. We first demonstrate an all-optical - and therefore non-destructive - technique for precisely locating a QD in a section of the antenna. The position of the emitter is important because it conditions the strength of the light-matter interaction within the antenna, as well as the coupling of the QD to certain spectral decoherence channels. The proposed technique exploits the emission of the QD in two guided modes which present different spatial profiles and is based on a measurement of the angle-resolved far-field map. The second study focuses on spin-flip mechanisms that couple the exciton states of a neutral QD. These spin-flips are a source of decoherence. To reveal them, we integrate the QD into an anisotropic photonic structure (here a photonic wire with an elliptical cross section). Polarization measurements combined with time-resolved measurements of the photoluminescence decay then allow determining the spin-flip rates. We present a study of the influence of the temperature and of the non-resonant excitation power.

Quantum dot, Photonic wire antenna, Fourier microscopy, Exciton spin-flip

On-line thesis.