Microscopic description of tunnel-injection quantum-dot lasers

该项目的目标是推进半导体激光器的设计，这种激光器有可能极大地改善用于互联网的基于光纤的光数据通信。该设计基于以量子点(QD)为活性材料的隧道注入(TI)结构，有望极大地提高调制速度。设计的挑战在于不同纳米结构组件之间的相互作用：非均匀加宽的量子点系综、TI势垒和用于载流子注入的块状势垒材料。这种设备背后的物理原理有几个要求很高的方面。载流子传输连接了三维、二维和零维结构，这些结构之间的载流子散射过程受多体效应控制，而器件性能取决于存在隧道势垒时载流子动力学和增益特性之间的相互作用。该领域的领先科学家组成的联盟，以约翰·彼得·雷斯迈尔(Univ.Peter Reithmaier)为代表。Kassel)、Grzegorz Sęk(弗罗茨瓦夫理工大学)和Gadi Eisenstein(以色列理工学院)目前正在进行高速TI-QD激光器的实验实现及其各种光谱方法的表征。申请者已被邀请加入该联合体，该项目的结构目标是建立与所有三个团体进行新的直接合作的框架。在第一个资助期，在TI-QD-激光器的物理方面发现了新的和意想不到的结果。结果表明，由于纳米结构中的电子态混合和多体效应(极化子)，量子点能级排列的Lo声子共振条件被搁置。相反，发现了TI势垒的光谱过滤效应。只有将这种光谱滤光片与量子点发射体的不均匀展宽分布适当地对准，才能改善TI-QD激光器的调制特性。根据这些新的见解，在第二个应用阶段，新的激光结构将被生长和表征。同时，理论模型将被扩展，以进行直接的实验和理论比较。我们的目标是从微观上理解TI-QD激光器中设备运行的相关物理原理，并演示改进的发射过程。

The goal of this project is to advance the design of semiconductor lasers, which have the potential to strongly improve fiber-based optical data communication as used for the internet. The design is based on a tunnel-injection (TI) structure with quantum dots (QDs) as active material and promises strongly improved modulation speed. The challenge for the design lies in the interplay between different nanostructure components: the inhomogeneously broadened QD ensemble, the TI barrier, and the bulk barrier material used for carrier injection. The physics underlying such a device has several demanding aspects. Carrier transport connects three-, two-, and zero-dimensional structures, the carrier scattering processes between these structures is governed by many-body effects, and the device performance depends on the interplay between carrier dynamics and gain properties in the presence of a tunnel barrier. A consortium of leading scientists in this field, represented by Johann Peter Reithmaier (Univ. Kassel), Grzegorz Sęk (Wroclaw University of Technology) and Gadi Eisenstein (Technion, Israel Institute of Technology) is presently working on the experimental realization of high-speed TI-QD lasers and their characterization with various spectroscopic methods. The applicant has been invited to join this consortium and the structural goal of this project is to establish the framework for a new direct collaboration with all three groups. In the first funding period, new and unexpected results for the physics of TI-QD-lasers were discovered. The LO-phonon resonance condition for the alignment of QD levels turns out to be suspended by electronic state mixing in the nanostructure and many-body effects (polarons). Instead, a spectral filter effect of the TI-barrier was discovered. Only with proper alignment of this spectral filter to the inhomogeneous broadening distribution of the QD emitters the improved modulation properties of TI-QD lasers are expected. According to these new insights, during the second application period, new laser structures will be grown and characterized. In parallel, theoretical models will be expanded to conduct direct experiment-theory comparisons. Our goal is a microscopic understanding of the relevant physics underlying the device operation in TI-QD lasers and the demonstration of improved emission processes.