Ultrafast Dephasing of Strongly Coupled Plasmon-Exciton States

强耦合等离子体激子态的超快相移

• 批准号: 2304905
• 负责人: Gregory Hartland
• 金额: $ 62.5万
• 依托单位: University of Notre Dame
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-05-15 至 2026-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2304905&HistoricalAwards=false
• 关键词: Ultrafast; Dephasing; Strongly; Coupled; Plasmon

With support from the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) program in the Division of Chemistry, Professors Gregory Hartland and Masaru Kuno of the University of Notre Dame are using optical microscopy to study the propagation of exciton-plasmon polaritons in individual semiconductor-metal nanostructures. Polaritons are unusual states that are produced by coupling the surface plasmons created by optical excitation in metals to the excited states of molecules or semiconductors. Polaritons have very short lifetimes and move very quickly, making them difficult to study using conventional techniques. Professors Hartland, Kuno and their students will use sophisticated light scattering and ultrafast microscopy techniques to measure the lifetimes of exciton-plasmon polaritons, as well as the distances they travel along individual semiconductor-metal nanostructures. Discoveries from this project could lead to a better understanding of the properties of polaritons in nanomaterials, and new strategies for solar energy generation. High school teachers and students will be recruited for this project from the Penn-Harris-Madison School Corporation, a local school district with a population of approximately 12,000 students. They will participate in the light scattering experiments, as well as a proect to develop a low-cost microscope for detecting and characterizing microplastics in the environment. The project will contribute to the development of the Nation's scientific workforce in this way as well as by providing research opportunities for graduate and undergraduate students. To understand the properties of exciton-plasmon polaritons, and whether they can be used for applications such as solar energy conversion, it is important to understand their dynamics. Because the lifetimes of these states are typically very short (100 fs), they are challenging to measure. In this project the lifetimes of polariton states created by coupling propagating surface plasmons (PSPs) of single metal nanostructures to the exciton transitions of semiconductors will be investigated by light scattering and ultrafast transient absorption microscopy. In the light scattering experiments a combination of real space and back-focal plane imaging will be used to measure the propagation lengths and group velocities, respectively, of the exciton-PSP polariton states. These two quantities give the polariton lifetime. Importantly, these experiments can be used to interrogate systems with very short lifetimes. For systems where the dynamics are relatively slow (50-100 fs), the lifetimes will also be directly measured by ultrafast single-particle transient absorption experiments. Measurements will be performed for different semiconductors coupled to Ag or Au nanostructures, as well as for non-traditional plasmonic systems, such as titanium nitride (TiN). There are several technological broader impacts of the proposed work. For example, the propagation lengths for SPPs (surface plasmon polarities) are much longer than those for exciton states. Thus, coupling excitons to SPPs can significantly increase their propagation lengths, and potentially improve the performance of solar energy conversion devices.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在化学系化学结构、动力学和机制A （CSDM-A）项目的支持下，圣母大学的Gregory Hartland教授和Masaru Kuno教授正在使用光学显微镜研究激子-等离子体激子在单个半导体金属纳米结构中的极化传播。极化激子是由金属中的光激发产生的表面等离子体激元与分子或半导体的激发态耦合而产生的不寻常状态。极化子的寿命非常短，移动非常快，这使得它们很难用传统的技术来研究。Hartland教授、Kuno教授和他们的学生将使用复杂的光散射和超快显微镜技术来测量激子-等离子体激元的寿命，以及它们沿着单个半导体金属纳米结构行进的距离。这个项目的发现可能会让我们更好地理解纳米材料中极性的性质，并为太阳能发电提供新的策略。高中教师和学生将从宾夕法尼亚-哈里斯-麦迪逊学校公司（Penn-Harris-Madison school Corporation）招募，这是一个拥有约12,000名学生的当地学区。他们将参与光散射实验，以及开发用于检测和表征环境中微塑料的低成本显微镜的项目。该项目将以这种方式促进国家科学劳动力的发展，并为研究生和本科生提供研究机会。为了了解激子-等离子激元的性质，以及它们是否可以用于太阳能转换等应用，了解它们的动力学是很重要的。由于这些状态的寿命通常很短（100秒），因此测量它们具有挑战性。本项目将利用光散射和超快瞬态吸收显微镜研究单金属纳米结构的表面等离子体与半导体激子跃迁耦合产生的极化激子态的寿命。在光散射实验中，将采用实空间成像和后焦平面成像相结合的方法分别测量激子- psp极化激子态的传播长度和群速度。这两个量给出了极化子的寿命。重要的是，这些实验可以用来询问寿命很短的系统。对于动力学相对缓慢（50-100 fs）的系统，寿命也将通过超快单粒子瞬态吸收实验直接测量。测量将执行不同的半导体耦合到Ag或Au纳米结构，以及非传统的等离子体系统，如氮化钛（TiN）。拟议的工作有几个技术上更广泛的影响。例如，SPPs（表面等离子激元极性）的传播长度比激子态的传播长度长得多。因此，将激子与spp耦合可以显著增加其传播长度，并有可能提高太阳能转换装置的性能。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。