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978-3-8439-0947-1, Reihe Physik
Strong Photon-Photon Interactions in Solid State Cavity QED
168 Seiten, Dissertation Eidgenössische Technische Hochschule (ETH) Zürich (2013), Softcover, A5
This dissertation reports experiments investigating photon-photon interactions in a solid-state cavity-quantum electrodynamics (cavity-QED) setting. We study low-dimensional quantum-photonic systems, namely single quantum dots (QDs) and quantum wells (QWs) strongly-coupled to nano- and microcavities, respectively.
A device consisting of a single self-assembled QD strongly-coupled to a photonic-crystal nanocavity is investigated under resonant-scattering spectroscopy. Unlike cold atoms in dilute gases self-assembled QDs are mesoscopic objects embedded in a semiconductor host material. Decoherence mechanisms such as charge fluctuations (blinking) in the QD occur, when probing the system optically. To counteract the blinking effect an optical re-pump technique is implemented.
Photon correlation measurements reveal strong antibunching of photons scattered off the system demonstrating the photon-blockade effect. This proves that our device enables strong photon-photon interactions. For particular laser-light detunings, significant photon bunching is observed, due to a direct two-photon transition to the second Jaynes-Cummings manifold.
These single-photon nonlinearities enable the implementation of a single-photon all-optical switch where a single control photon resonant with one of the fundamental polariton states enables the scattering of signal photons resonant with a transition from the first to the second Jaynes-Cummings manifold. By using appropriately tailored laser pulses, the switching speed of the device is shown to be on ultrafast timescales of about 50 ps. As an application, a single-photon pulse correlator working on these timescales is presented.
The second part of the thesis is devoted to a different cavity-QED setting based on the coupling of two-dimensional QW excitons to Fabry-Perot cavities. In contrast to monolithic cavities with little flexibility of tuning parameters, we present a new type of semi-integrated system consisting of a fiber-end mirror, which is approached to the surface of a chip-integrated semiconductor mirror with a QW layer on top. The curved fiber mirror ensures photonic-mode confinement without degrading the cavity-quality factor. In this fully-tunable system unprecedented polariton lifetimes of up to 100 ps are achieved. Moreover, when driving such a system with an off-resonant laser signatures of polariton lasing are observed for high powers.