Quantenoptische Effekte in Quantenpunkt-Mikroresonatoren

本项目的目的是发展半导体量子点的微观模型，这些量子点可以作为新型非经典光源的活性材料。对于原子系统，最近已经证明了一种超辐射激光，其中利用发射体的自发同步来显著提高发射的光谱纯度。同时，发射不是通过谐振器中的光子存储的，而是作为发射器的相干相位存储的。在这个项目中，将研究半导体量子系统的相应效应。在最近的文献中，可以找到一些理论和实验上的贡献，它们解决了量子点的超辐射耦合对光致发光性质的影响。在这个项目的前一阶段，在激光系统中也发现了明显的超辐射耦合的特征。理论和实验小组将直接合作来确定系统和激发条件，其中量子点发射体的超辐射耦合起着核心作用。在传统激光器中，量子点的激发是通过势垒态进行的。共振量子点激发可以强烈地减小系统的均匀线宽，当均匀线宽小于腔线宽时，可以达到原子系统的“坏腔区”，从而使原子系统出现超辐射激光。对于量子点系统，我们将研究超辐射效应是否能够克服非均匀展宽的不利影响。对于通过微腔交换光子的量子点，非共振的点-腔耦合效应可以缓解非均匀展宽，这是最近被探索的。此外，结合使用光抽运的相应实验研究，将讨论抽运光的光子统计(相干与热辐射)对发射特性的影响。在理论模型中，半导体特有的相互作用效应将在微观水平上被考虑。基于最近观察到的量子点激光器中发射体之间的超辐射耦合特征，将研究以下应用：产生具有超泊松统计特性的非经典光。利用发射体之间的集体耦合效应来降低激光阈值，用于更快的激光动力学，以及促进具有极低平均光子数的受激发射。由于超辐射量子点耦合而产生的发射的相干特性得到改善。具有改进的相干特性或非经典光子统计的光源可以用于基本量子光学效应以及在量子信息技术中的应用。

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.