Quantum dot micropillars
This topical review provides an overview of quantum dot micropillars and their application in cavity quantum electrodynamics (cQED) experiments. The development of quantum dot micropillars is motivated by the study of fundamental cQED effects in solid state and their exploitation in novel light sources. In general, light–matter interaction occurs when the dipole of an emitter couples to the ambient light field. The corresponding coupling strength is strongly enhanced in the framework of cQED when the emitter is located inside a low mode volume microcavity providing three-dimensional photon confinement on a length scale of the photon wavelength. In addition, coherent coupling between light and matter, which is essential for applications in quantum information processing, can be achieved when dissipative losses, predominantly due to photon leakage out of the cavity, are strongly reduced. In this paper, we will demonstrate that high-quality, low mode volume quantum dot micropillars represent an excellent system for the observation of cQED effects. In the first part the fabrication and the technological aspects of quantum dot micropillars will be discussed with a focus on the AlGaAs material system. The discussion involves the epitaxial growth and the processing of optically as well as electrically driven micropillar structures. Moreover, micropillars realized in alternative material systems and other resonator geometries will be addressed briefly. The second part will focus on the optical characterization of micropillar cavities with respect to their mode structure and the quality ( Q ) factor for different device geometries and resonator layouts. In the final part, we will present cQED experiments with quantum dot micropillars. Here, weak and strong coupling effects in the framework of cQED will be presented. These effects are strongly related to possible applications of quantum dot micropillars, such as single photon sources and low threshold microlasers, which will also be discussed. The paper will close with an outlook on current and future developments and a summary.