Quantenoptische Effekte in Quantenpunkt-Mikroresonatoren

• Applicant: Professor Dr. Frank Jahnke
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2010 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 167776844

The aim of this project is the development of microscopic models for semiconductor quantum dotswhich can be used as active material in novel non-classical light sources. For atomic systems,recently a superradiant laser has been demonstrated in which a spontaneous synchronization ofthe emitters is utilized to strongly increase the spectral purity of the emission. At the same time, theemission was not stored via photons in the resonator, rather than as a coherent phase of theemitters. Within this project, the corresponding effects will be studied for semiconductor quantumdotsystems. In the recent literature, several theoretical and experimental contributions can befound, which address the influence of superradiant coupling of quantum dots onphotoluminescence properties. In the past phase of this project, clear signatures of superradiantcoupling also have been found in laser systems.A direct collaboration between theoretical and experimental groups will be used to identify systemsand excitation conditions, in which superradiant coupling of quantum-dot emitters plays a centralrole. In conventional lasers the excitation of quantum dots takes place via barrier states. Thesubsequent relaxation leads to dephasing, which drives the system into the incoherent regime.Resonant quantum-dot excitation can be used to strongly reduce the homogeneous line width.When the latter is smaller than the cavity line width, the "bad-cavity regime" can be reached, forwhich atomic systems can show superradiant lasing. For the quantum-dot system we will studywhether superradiant effects are able to overcome the detrimental influence of inhomogeneousbroadening. For quantum dots exchanging photons via a microcavity, the inhomogeneousbroadening is mitigated by off-resonant dot-cavity coupling effects, which have been recentlyexplored. Furthermore, in connection with the corresponding experimental studies using opticalpumping, the influence of the photon statistics of the pump light (coherent vs. thermal radiation) onthe emission properties will be addressed. In the theoretical models, semiconductor specificinteraction effects will be considered on a microscopic level.Based on the recently observed signatures of superradiant coupling between the emitters inquantum-dot lasers, the following applications will be studied:Generation of non-classical light with Super-Poisson-Statistics.Use of collective coupling effects between emitters for a laser-threshold reduction, for fasterlaser dynamics, as well as to facilitate stimulated emission with very low mean photon number.Improved coherence properties of the emission due to superradiant quantum-dot coupling.Light sources with improved coherence properties or non-classical photon statistics can be used infundamental quantum-optical effects as well as for applications in quantum informationtechnologies.

• DFG Programme: Research Grants