An integrated semiconductor platform for the implementation and study of higher-order exceptional points

将开放波或量子系统的基本概念转移到高度集成的固态器件，对于更深入地理解基础物理学和创新新技术和器件都至关重要。 近年来，非厄米系统成为焦点，包括那些表现出宇称时间对称性。引起人们兴趣的主要原因是参数空间中所谓的例外点（EP），这是两个或多个能量本征值和相应本征态合并的奇异简并。在一系列有趣的基本方面中，这些简并对于超灵敏传感设备具有巨大的潜力。潜在地，当从二阶EP到n阶EP时甚至更是如此，其中n个能量本征值和-态合并。这个跨学科的研究项目位于实验固态光学和理论非厄米光子学之间的边界。马格德堡小组将使用耦合模理论和数值模拟来奠定基础并建立理论骨干，以获得适用于（高阶）EP的参数集并评估模拟设备的传感潜力。维尔茨堡集团将利用其在半导体外延和器件制造方面的专业知识，实现基于可缩放III-V族材料的定制EP器件。器件的制造和优化将与数值模拟密切相关，并以迭代的方式有效地进行。该项目的目标是开发一个强大的和多功能的集成半导体平台，允许联合收割机的概念，EP的机制，用于创建所谓的特殊表面的参数空间和由此产生的强大的EP。利用大规模器件表征技术和激光扫描技术，我们将绘制出实验参数空间，并实现二阶和三阶EP耦合到合适的总线波导的环形激光器件。我们将使用复杂的光谱技术来表征制造的器件特性，证明所需的n次方根缩放系统响应扰动。使用人工散射体-光刻定义和移动的-我们将探索这些可缩放设备的传感能力。在项目的后期阶段，我们将把注意力转向绘制EP附近的能量表面。在这样做的过程中，我们将获得宝贵的洞察力，但尚未很好地理解周围的高阶EP的拓扑结构，这将连接我们的研究，拓扑光子学的令人兴奋的新领域。

The transfer of basic concepts of open wave or quantum systems to highly integrated solid-state devices is of paramount importance both for a deeper understanding of the underlying physics and for the innovation of new technologies and devices. In recent years, non-Hermitian systems came into focus including those exhibiting parity-time symmetry. The main reason for the rising interest are so-called exceptional points (EPs) in parameter space, which are exotic degeneracies at which two or more energy eigenvalues and the corresponding eigenstates coalesce. Among a range of interesting fundamental aspects, these degeneracies have great potential for ultrasensitive sensing devices. Potentially, even more so when going from second-order EPs to EPs of nth order, where n energy eigenvalues and -states coalesce. This interdisciplinary research project is positioned at the border between experimental solid-state optics and theoretical non-Hermitian photonics. The Magdeburg group will lay the groundwork and establish the theoretical backbone using coupled-mode theory and numerical simulations to obtain parameter sets suitable for (higher-order) EPs and to evaluate the sensing potential of simulated devices. The Würzburg group will use its expertise in semiconductor epitaxy and device fabrication to realize tailored EP-devices based on scaleable group-III-V materials. The device fabrication and optimization will be closely tied to the numerical simulations and performed efficiently in an iterative way. The goal of this project is to develop a robust and versatile integrated semiconductor platform that allows to combine the concept of EPs with the mechanism for the creation of so-called exceptional surfaces in parameter space and the resulting robust EPs. Using large scale device characterization techniques and laser scanning techniques we will map out the experimental parameter space and realize second- and third-order EPs in ring laser devices coupled to suitable bus waveguides. We will use sophisticated spectroscopic techniques to characterize the fabricated device properties, demonstrating the desired nth-root scaling of the systems response to perturbations. Using an artificial scatterer – both lithographically defined and mobile – we will explore the sensing capabilities of these scaleable devices. In a later stage of the project we will turn our attention to mapping the energy surfaces in the vicinity of the EPs. In doing so, we will get valuable insight into the yet not well understood topology around higher-order EPs, which will connect our research to the exciting new field of topological photonics.