Microscopic theory of light emission from semiconductor quantum dots in microcavities

在过去的十年里，半导体微腔被成功地用于研究基本的光物质效应。以往的研究主要采用量子阱作为有源材料，布拉格反射镜作为一维腔体。我们的目标是将这些研究扩展到两个方向：i)在量子阱纳米结构中，载流子的本征相互作用过程(特别是库仑相互作用)也主导着光与物质的相互作用。将半导体量子点用于活性材料允许修改这些相互作用过程，并且电子态的离散性质是新的光-物质相互作用效应的关键，所述新的光-物质相互作用效应涉及例如单个或少数光子。Ii)为了实现与量子点的强耦合，三维光子禁闭是必要的。此外，三维光子限制强烈地增加了自发辐射耦合，从而增强了光发射中的量子效应。微观理论将被用来研究半导体微腔中量子点的发射特性。从量子点的电子态出发，研究电子弛豫过程及其对激子性质(低激发区)和光学增益(高激发区)的影响。半导体微腔的三维模式结构的计算将被用来确定在弱耦合区域中改变的自发辐射性质。此外，在光-物质相互作用的量子力学理论中，将研究光发射的统计特性。对于大自发辐射耦合，我们将研究耦合腔--量子点系统中的强度-强度关联。在弱激发极限下，我们将直接与本课题组的实验研究合作，分析双激子-激子跃迁产生纠缠光子等量子光学效应。

Semiconductor microcavities have been successfully used in the past decade to study fundamental light-matter effects. Previous investigations mainly used quantum wells as active material and Bragg mirrors for a one-dimensional cavity. Our goal is to extend these investigations in two directions: i) In quantumwell nanostructures, the intrinsic interaction processes of carriers (especially the Coulomb interaction) dominate also the light-matter interaction. The use of semiconductor quantum dots for the active material allows to modify these interaction processes and the discrete nature of the electronic states is the key for new light-matter interaction effects involving, e.g., single or few photons. ii) A three-dimensional photonic confinement will be necessary to realize the strong-coupling regime with quantum dots. Furthermore, the three-dimensional photon confinement strongly increases the spontaneous emission coupling which enhances quantum effects in the light emission. A microscopic theory will be used to study the emission properties of quantum dots in semiconductor microcavities. Starting from the electronic states of the quantum dots, electronic relaxation processes and their influence on the excitonic properties (in the low-excitation regime) and on the optical gain (under high-excitation conditions) will be studied. Calculations of the three-dimensional mode structure of semiconductor microcavities will be used to determine the altered spontaneous emission properties in the weak-coupling regime. Furthermore, within a quantum mechanical theory of the light-matter interaction, statistical properties of the light-emission will be investigated. For large spontaneous-emission coupling intensity-intensity correlations in the coupled cavity--quantum-dot system will be studied. In the weak excitation-limit quantumoptical effects like the creation of entangled photons for the biexciton-exciton transition will be analyzed in direct collaboration with the experimental investigations of our research group.