Utilizing a nanoantenna for ultrafast spectroscopy of a single semiconductor nanocrystal

半导体纳米结构具有迷人的光学特性。电子的强约束导致了大的量子化效应。胶体纳米晶体在光伏和量子光学等多个领域都有应用。为了详细了解光物理，我们需要单纳米晶体水平上的光谱学，否则系综平均将模糊许多方面。单一胶体的线性光谱是一种成熟的技术，但电荷分离的超快动力学只能通过非线性光谱来获得。然而，由于非线性效应的相互作用截面小，对单个胶体进行超快光谱分析是目前不可能完成的任务。在这里，我建议使用光学纳米天线来增强光-物质相互作用。正如我们所展示的单个金属纳米颗粒的瞬态吸收，一个简单的等离子体天线已经可以将非线性响应提高10倍。在目前的项目中，我们希望以此为基础。由于天线的增强，单纳米晶体的非线性光谱将首次成为可能。这将使我们能够研究激发后不久的电子动力学，它负责光伏电池中的电荷转移和量子比特中纳米晶体的相干操作。

Semiconductor nanostructures show fascinating optical properties. The strong confinement of the electrons leads to large quantization effects. Colloidal nanocrystals find applications in diverse fields such as photovoltaics and quantum optics. For a detailed understanding of the photophysics we need optical spectroscopy on the level of single nanocrystals, as otherwise the ensemble average will blur many aspects. Linear spectroscopy of a single colloid is a well established technique, but the ultrafast dynamics of charge separation can only be obtained by nonlinear spectroscopy. However, for a single colloid ultrafast spectroscopy is an impossible task up to date, due to the small interaction cross sections for nonlinear effects. Here, I propose to employ an optical nanoantenna to enhance the light-matter interaction. As we have shown for the transient absorption of a single metal nanoparticle, already a simple plasmonic antenna can enhance the nonlinear response by a factor of 10. In the present project we want to build on this. For the first time, nonlinear spectroscopy of single nanocrystal will become possible due to antenna enhancement. This will allow us to investigate electron dynamics shortly after excitation which is responsible for charge transfer in photovoltaics and the coherent operation of the nanocrystals in a quantum bit.