The super-thermal photon bunching in quantum-dot (QD) micropillar lasers is investigated both experimentally and theoretically via simulations driven by dynamic considerations. Using stochastic multi-mode rate equations we obtain very good agreement between experiment and theory in terms of intensity profiles and intensity-correlation properties of the examined QD micro-laser's emission. Further investigations of the time-dependent emission show that super-thermal photon bunching occurs due to irregular mode-switching events in the bimodal lasers. Our bifurcation analysis reveals that these switchings find their origin in an underlying bistability, such that spontaneous emission noise is able to effectively perturb the two competing modes in a small parameter region. We thus ascribe the observed high photon correlation to dynamical multistabilities rather than quantum mechanical correlations.

Microlasers are ideal candidates to bring the fascinating variety of nonlinear complex dynamics found in delay-coupled systems to the realm of quantum optics. Particularly attractive is the possibility of tailoring the devices' emission properties via non-invasive delayed optical coupling. However, until now scarce research has been done in this direction. Here, we experimentally and theoretically investigate the effects of delayed optical feedback on the mode-switching dynamics of an electrically driven bimodal quantum-dot micropillar laser, characterizing its impact on the micropillar's output power, optical spectrum and photon statistics. Feedback is found to influence the switching dynamics and its characteristics time scales. In addition, stochastic switching is reduced with the subsequent impact on the microlaser photon statistics. Our results contribute to the comprehension of feedback-induced phenomena in micropillar lasers and pave the way towards the external control and tailoring of the properties of these key systems for the nanophotonics community.

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X-ray microscopy in the water window has become a valuable imaging tool for a wide field of applications with a resolution in the nanometer regime. The emergence and the development of laboratory based transmission X-ray microscopes (LTXM) can be of great benefit to users, since LTXM provides access to a method previously limited to synchrotron facilities only. In recent years, measuring times in the laboratory have been reduced to the point, where tomography of aqueous cryofixated samples has become feasible.We report on a laboratory full-field transmission X-ray microscope based on a laser induced plasma source located at the Berlin Laboratory for innovative X-ray Technologies. A short introduction on full-field X-ray microscopy in the water window is given.We demonstrate that, with a thin disk laser-system (TDL), which provides an average power of ~15 W a spatial resolution of ∆x = 41 nm ± 3 nm (half-pitch) is feasible. An image of a diatom recorded at 15 W average laser power with a magnification of 1125x captured in 5 min is presented.

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