ISBN 978-3-8439-3146-5

978-3-8439-3146-5, Reihe Physik

Fabian Hargart
Enhanced light-matter interaction with semiconductor quantum dots in single and double cavity structures

231 Seiten, Dissertation Universität Stuttgart (2017), Softcover, A5

Zusammenfassung / Abstract

The work at hand investigates several types of light-matter interactions using semiconductor quantum dots (QDs) embedded into different microcavity structures. Photons are characterized by their small interaction cross-section and small dephasing, making them uncontroversially to the particle of choice for long-range communication and the interconnection of distant quantum nodes. The intrinsically weak interaction of flying and stationary qubits can be efficiently increased by trapping and storing photons in light-confining structures. Semiconductor microcavities offer high optical qualities and easy handling in combination with deterministic fabrication and scalability. The integrated QDs feature strong oscillator strengths, beneficial for high coupling rates. Within the context of cavity quantum electrodynamics a number of experiments reported on enhanced extraction efficiencies, reduced emitter lifetimes and strongly coupled QD-cavity systems.

A large part of this work is devoted to the investigation of different regimes of strong-field light-matter interaction with few cavity photons. The cavity is therefore coherently driven by a resonant laser and the systems response is recorded by means of photoluminescence spectroscopy. The occurrence of dressed states and the observation of Mollow triplet sidebands is achieved for a single photon in the cavity. In the asymptotic limit of large QD-cavity detuning, the AC Stark effect is statistically investigated for more than 400 QDs in 15 micropillar cavities. The detuning dependence is extracted and reflects the expected reciprocally proportional behavior. A unique set of light and matter states is created by continuously driving the two-photon transition of the QD biexciton state. The emergence of multiple splitted emission lines proofs the strongly coupled light-matter regime, analog to the Mollow triplet ladder. An intuitive model of a dressed 4-level atom is presented to explain the basic experimental results and to estimate the mixture of the occurring states.

The second part aimes at radiative coupling between two distant QDs located in different disks of a double microcavity structure. We apply different schemes of confocal microscopy to identify ab initio, but weakly coupled microdisk pairs and locate resonant QDs within. The measurements reveal single-photon emission of an indirectly excited emitter. First results indicate on-chip resonant Rayleigh scattering of single-photons emitted by a QD.