We report on the deterministic fabrication of sub-µm mesa-structures containing single quantum dots (QDs) by in-situ electron-beam lithography. The fabrication method is based on a twostep lithography process: After detecting the position and spectral features of single InGaAs QDs by cathodo-liminescence (CL) spectroscopy, circular sub-um mesa-structures are defined by highresolution electron-beam lithography and subsequent etching. Micro-photoluminscence spectroscopy demonstrates the high optical quality of the single-QD mesa-structures with emission linewidths below 15 µeV and g (2) (0) = 0.04. Our lithography method has an alignment precision better than 100 nm which paves the way for a fully-deterministic device technology using in-situ CL lithography.

The regime of strong light-matter coupling is typically associated with weak excitation. With current realizations of cavity-QED systems, strong coupling may persevere even at elevated excitation levels sufficient to cross the threshold to lasing. In the presence of stimulated emission, the vacuumRabi doublet in the emission spectrum is modified and the established criterion for strong coupling no longer applies. We provide a generalized criterion for strong coupling and the corresponding emission spectrum, which includes the influence of higher Jaynes-Cummings states. The applicability is demonstrated in a theory-experiment comparison of a few-emitter quantum-dot-micropillar laser as a particular realization of the driven dissipative Jaynes-Cummings model. Furthermore, we address the question if and for which parameters true single-emitter lasing can be achieved, and provide evidence for the coexistence of strong coupling and lasing in our system in the presence of background emitter contributions.

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We measure the full photon-number distribution emitted from a Bose condensate of microcavity exciton polaritons confined in a micropillar cavity. The statistics are acquired by means of a photon-number-resolving transition edge sensor. We directly observe that the photon-number distribution evolves with the nonresonant optical excitation power from geometric to quasi-Poissonian statistics, which is canonical for a transition from a thermal to a coherent state. Moreover, the photon-number distribution allows one to evaluate the higher-order photon correlations, shedding further light on the coherence formation and phase transition of the polariton condensate. The experimental data are analyzed in terms of thermal-coherent states, which gives direct access to the thermal and coherent fraction from the measured distributions. These results pave the way for a full understanding of the contribution of interactions in light-matter condensates in the coherence buildup at threshold.

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