Understanding and controlling optical excitations in individual hybrid nanostructures

混合纳米结构是由两种或两种以上的纳米材料组合而成的一种新的异质结构，它在光采集、量子点激光、化学和生物传感以及量子计算等领域有着广泛的应用前景。这种兴趣是由两个纳米级材料系统的集成可以导致结构表现出新的特性，如增强的光致发光、化学活性或载流子转移，这是由单个组件之间的耦合引起的。例如，金属和半导体是两类具有非常不同性质的材料，将它们结合起来形成混合纳米材料是一个基本的兴趣。金属可以在纳米尺度上限制光，而半导体提供开关功能，它们的组合有望实现高密度超快纳米光子集成电路。因此，开发和控制在杂化纳米结构中发现的潜在独特性能需要对杂化成分材料之间的耦合有透彻的了解。智力优势-本建议侧重于探索两种共同感兴趣的特定杂化材料系统的基本微观机制，即：(1)通过隧道耦合的量子点/量子阱半导体杂化纳米结构和(2)通过激子和等离子体共振耦合的金属/半导体杂化纳米结构。本研究的目的是阐明在定义良好的纳米尺度混合纳米结构中控制光响应和能量转移的机制。在这些系统中建立结构和功能之间的关系将导致颠覆性的新知识，并对一系列应用产生影响，包括等离子体和量子点激光器，生物传感器和能量转换。该方案的核心创新在于新型纳米级混合结构和结构的制造、光学探测和模拟，其几何参数可以系统地调谐。探索这些混合材料系统需要在纳米制造、相干光谱学和理论建模方面共同努力，这是美国和德国研究团队提出国际合作的根本原因。美国团队由阿肯色大学的研究人员组成，他们是俄克拉荷马大学在美国国家科学基金支持的材料研究科学与工程中心的合作伙伴。该团队在分子束外延生长，扫描隧道显微镜表征，纳米结构的光学行为及其相互作用表征方面尤其有天赋。德国团队由奥尔登堡大学<s:1>物理研究所（Institut r Physik）的研究人员组成，他们在开发和应用超快和纳米级光学光谱工具来研究单纳米结构和混合纳米结构阵列的相干光学行为方面拥有多年经验。这两个团队共同拥有丰富的经验、才能和基础设施，在理解混合纳米结构中耦合的材料科学和物理方面开辟了新的领域。在过去一年半的时间里，两个团队之间的互访以及最近的合作出版物证明了强大团队合作的潜力已经开始形成。更广泛的影响-从纯粹的技术角度来看，该建议为详细微观理解半导体量子点或激子的基本光学激发与金属纳米粒子（MNP）或表面等离子激元极化子的基本光学激发之间的相互作用以及单个量子点和量子阱之间的相干和非相干共振耦合提供了机会。此外，由于学生最终将在全球市场工作，因此没有比国际合作更好的准备了。通过与国际规模的团队合作，学生的团队合作增加了一个新的维度，要求学生处理远程、跨文化和语言挑战的合作。作为该提案的一部分，提出了一项针对美国和德国K-12学生的积极推广计划，这将进一步为文化共享提供机会。并讨论了多样性的进展和计划。

Hybrid nanostructures, the combination of two or more nanoscale materials to form a new heterostructure, are being actively pursued for a number of potential applications including lightharvesting, quantum dot lasers, chemical and biological sensing, and quantum computation. This interest is driven by the fact that the integration of two nanoscale material systems can lead to structures that exhibit novel properties, such as, enhanced photoluminescence, chemical activity, or carrier transfer, which result from the coupling between the individual components. For example, metals and semiconductors are two classes of materials with very different properties and combining them to form hybrid nanomaterials is of fundamental interest. Whereas metals can confine light on the nanoscale, semiconductors provide switching functionality and their combination promises high-density ultrafast nanophotonic integrated circuitry. Consequently, however, the development and control of the potentially unique properties found in hybrid nanostructures requires a thorough understanding of the coupling between the hybridized component materials.Intellectual Merit - This proposal focuses on exploring the fundamental microscopic mechanisms governing the optical excitations of two specific hybrid material systems of common interest, namely (1) quantum-dot/quantum-well semiconductor based hybrid nanostructures coupled via tunneling and (2) metal/semiconductor hybrid nanostructures coupled via their exciton and plasmon resonances. The goal of the proposed research is to elucidate the mechanisms governing the optical response and energy transfer in well-defined nanoscale hybrid nanostructures. Establishment of the relationships between structure and function in these systems would lead to disruptive new knowledge with impact on a range of applications, including plasmonic and quantum dot lasers, biosensors, and energy conversion. The core innovation in this proposal lies in the fabrication, optical probing and simulation of novel nanoscale hybrid structures and architectures whose geometrical parameters can be systematically tuned.Exploring these hybrid material systems requires a concerted effort in nanofabrication, coherent optical spectroscopy and theoretical modeling, a fundamental reason for proposing an international collaboration between an American and German research team. The American team consists of researchers at the University of Arkansas who are partners with the University of Oklahoma in an NSFsupported Materials Research Science and Engineering Center. This team is especially talented in the growth by molecular beam epitaxy, characterization by scanning tunneling microscopy, and the characterization of the optical behavior of nanostructures and the interactions between them. The German team consists of researchers at the Institut für Physik, at the University of Oldenburg, who have many years of experience in the development and application of ultrafast and nanoscale optical spectroscopy tools to study the coherent optical behavior of both single and arrays of hybrid nanostructures. Together, both teams have the experience, talent, and infrastructure to break new ground in the understanding of the material science and physics of coupling in hybrid nanostructures. The potential for a strong team effort, which has already begun to form over the last year and a half, is evidenced by exchange visits between both teams as well as recent collaborative publication.Broader Impact – From a purely technical point of view, this proposal presents an opportunity for the development of a detailed microscopic understanding of the interactions between the elementary optical excitations of a semiconductor quantum dot, or exciton, and the elementary optical excitation of a metal nanoparticle (MNP), or surface plasmon polariton, as well as the coherent and incoherent resonant coupling between a single quantum dot and quantum well.In addition, since students will eventually work in a global market there is no better preparation for international collaboration than … international collaboration. By working with a team on an international scale there is a new dimension added to student teamwork, requiring students to handle collaboration that is remote, cross-cultural, and linguistically challenging. As part of this proposal an aggressive outreach plan to both K-12 American and German students is presented that will further provide an opportunity for the sharing of cultures. The progress and plans for diversity is also discussed.