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Fabrication and properties of GaAs microlenses with embedded InGaAs quantum dots / submitted by Stefanie Siebeneichler
AutorInnenSiebeneichler, Stefanie
Beurteiler / BeurteilerinRastelli, Armando
ErschienenLinz, 2017
Umfangx, 51 Seiten : Illustrationen
HochschulschriftUniversität Linz, Masterarbeit, 2017
Schlagwörter (DE)Mikrolinsen / Galliumarsenid / Quantenpunkte
Schlagwörter (EN)microlenses / gallium arsenide / quantum dots
Schlagwörter (GND)Galliumarsenid / Mikrolinse / Quantenpunkt
URNurn:nbn:at:at-ubl:1-15062 Persistent Identifier (URN)
 Das Werk ist gemäß den "Hinweisen für BenützerInnen" verfügbar
Fabrication and properties of GaAs microlenses with embedded InGaAs quantum dots [19.73 mb]
Zusammenfassung (Englisch)

Sources of single and entangled photons on demand are attracting strong attention, in view of their potential applications in emerging quantum technologies. In this context, semiconductor quantum dots are considered the most promising systems. Since quantum dots are embedded in a high-refractive-index matrix, efficient light extraction requires proper molding of the semiconductor structures. Several strategies have been pursued to integrate quantum dots in photonic structures. These include photonic crystal and pillar microcavities, photonic wires, as well as microlenses. Compared to microcavities, which require precise matching of the quantum dot emission and cavity mode, photonic wires and microlenses present the advantage of broad-band enhancement of the extraction efficiency. This is particularly relevant for sources of non-degenerate entangled photon pairs. In this thesis I present a novel and simple approach to fabricate dome-like shaped, monolithic GaAs microlenses by a two-step wet-etching process. The lenses are etched from a planar optical cavity containing randomly distributed InGaAs QDs with a gold back-mirror, which makes this the first successful implementation of microlenses featuring a gold mirror. Moreover, the gentle fabrication method will make it possible to integrate them even on fragile devices, such as microma- chined piezo-electric actuators, which have been recently developed by our group to precisely tune the emission properties of quantum dots. The functionality of the fabricated lenses was tested by micro-photoluminescence (-PL) spectroscopy at cryogenic temperatures. By measuring the excitonic emission of several tens of QDs at saturation, we found an increase in brightness with respect to a planar cavity. Further, a slight blue-shift of the exciton energy, a random change in in the fine-structure-splitting (FSS) of the neutral exciton and the appearance of partial polarization of the exciton emission were observed. All three observations were attributed to strain effects induced by the processing. Additionally, finite-element-method (FEM) simulations based on the measured lens shape showed an enhanced extraction efficiency with respect to a planar cavity, consistent with the experimental results.

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