Licht-Materie-Wechselwirkung in Halbleiter-Nanostrukturen zur Erzeugung nichtklassischen Lichts und stimulierter Emission

Abstract

The framework of quantum optics was developed side by side with groundbreaking experiments involving lasers and atoms as active medium. The amount of control one nowadays has on the design of semiconductor nanostructures is constantly leading to new progress in this field, and we can use quantum dots (QDs) that possess atom-like discrete states as emitters instead. With a single QD in a high-quality cavity with three-dimensional mode confinement, the ultimate limit of miniaturization is reached, where one electronic transition interacts with a single mode of the electromagnetic field. The application potential of this system lies in efficient light sources, new devices for quantum information technologies, as well as in highly tunable platforms to perform fundamental studies in the field of semiconductor quantum optics. We investigate the characteristics of microcavity lasers with single QD gain and discuss the possibility to realize stimulated emission in the strong-coupling regime. The impact of non-resonant background emitters present in experimental realizations is addressed, where off-resonant coupling between emitter resonances and the cavity mode is enabled via phonons or additional carriers in delocalized states. Furthermore, new schemes for electrically driven single-photon sources and the generation of polarization-entangled photons are proposed. Our theoretical analysis is based on microscopic theories going beyond simple atomic models. This allows us to investigate many-body effects and incorporates carrier-photon correlations, providing direct access to the statistical properties of the emission. The dynamical evolution of the system is described by means of density matrix approaches, or relies on cumulant expansion techniques where the first is numerically not possible. Multi-exciton effects of the quantum dot carriers play an important role, as well as the coupling to continuum states of the embedding material.