Cavity quantum electrodynamics is widely used in many solid-state systems for improving quantum emitter performances or accessing specific physical regimes. For these purposes it is fundamental that the non-classical emitter, like a quantum dot or an NV center, matches the cavity mode, both spatially and spectrally. In the present work, we couple single photons stemming from In(Ga)As quantum dots into an open fiber-based Fabry-Pérot cavity. Such a system allows for reaching an optimal spatial and spectral matching for every present emitter and every optical transition, by precisely tuning the cavity geometry. In addition to that, the capability of deterministically and repeatedly locating a single quantum dot enables to compare the behavior of the quantum emitter inside the cavity with respect to before it is placed inside. The presented open-cavity system shows full flexibility by precisely tuning in resonance different QD transitions, namely excitons, biexcitons and trions. A measured Purcell enhancement of 4.4 ± 0.5 is obtained with a cavity finesse of about 140, while still demonstrating a single-photon source with vanishing multi-photon emission probability.
Publication: Pure single-photon emission from In(Ga)As QDs in a tunable fiber-based external mirror microcavity
T. Herzog, M. Sartison, S. Kolatschek, S. Hepp, A. Bommer, C. Pauly, F. Mücklich, C. Becher, M. Jetter, S. L. Portalupi and P. Michler 
Quantum Sci. Technol 3, 034009 (2018)
Focus on Quantum Photonics: Chips and Dots
Contact person: T. Herzog