手性等离子体纳米结构的飞秒光学表征及其光子学应用

Optical chirality of plasmonic nanostructures has aroused great interest for their promising potential applications in optics, chemistry, and biosensing. Recent studies are mainly focused on construction of chiral structures and their optical activity. The determination of optical activity through circular dichroism (CD) spectroscopy has been served as a routine method for obtaining structural information. However, the steady state CD spectroscopy is not enough for observation of ultrafast structural changes such as those occurring during asymmetric chemical reactions. Thus femtosecond characterization is necessary for this purpose. Moreover, the ultrafast nonlinear optical response of gold nanoparticles under femtosecond laser paves the way for developing ultrafast all-optical switching. The introduction of chirality makes it possible to modulate circular polarized light in ultrafast time scale. This project is centered on the investigation of ultrafast nonlinear optical response of chiral plasmonic nanostructures experimentally and theoretically. The physical mechanisms of three typical chiral plasmonic nanostructures are then figured out. Finally the project will be focused on developing circular ultrafast all-optical switching based on the ultrafast optical responses of chiral plasmonic nanostructures.

手性等离子体纳米结构由于其在化学、生物及物理方面的巨大潜在应用价值，引起了科学家的广泛关注和研究。目前相关方面的研究大多集中在手性结构的构筑以及稳态圆二色光谱性质方面，其在超快脉冲激光下的飞秒表征还鲜有介绍。然而时间分辨的超快光学性质具有极大的科学研究价值，一方面有助于从根本上了解化学反应过程中结构的超快变化以及手性催化中电子的转移过程；另一方面，贵金属纳米粒子由于其超快非线性光学性质而表现出的介电常数在超短时间内的变化，使其成为实现超快全光调制开关的优选材料，同时手性的引入使得对圆偏振光的超快调制成为可能，为发展超快光子学偏振器件提供了一种新颖可行的思路。本项目将围绕手性等离子体纳米结构的超快光学性质来展开工作，结合实验与理论计算，系统深入地探讨其超快光谱特性及其物理机制，并研究其在超快光子学偏振器件上的应用。

本项目围绕等离激元纳米结构中热电子的超快动力学过程以及如何增强热电子的产生和转化效率开展了系列创新性研究。从研究单分散的金纳米粒子在超快飞秒脉冲下的热电子动力学弛豫性质出发，通过构筑不同种类的等离激元纳米结构如组装结构、光学谐振腔以及手性等离激元纳米结构等，实现了热电子产生和转化效率的增强，揭示了热电子弛豫的微观物理机制，并完成了热电子在光催化和超快光学开关、调制器等光学器件领域的初步应用探索。

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