有机/贵金属低维结构的可控构筑与光学特异性研究

Modern semiconductor-based electronics is rapidly approaching fundamental limits caused by interconnect delay and large heat generation. Photonics offers an effective solution to this problem by implementing optical communication systems based on optical waveguides and photonic circuits; because photons have intrinsically higher information-carry capacity and produce low heat loads. Unfortunately, the micrometer-scale bulky components of photonics restricted by diffraction limit have limited the hybrid integration of these components into electronic chips, which are now measured in nanometers. Surface plasmons (SPs) are light waves that occur at metal/dielectric interfaces, where a group of electrons is collectively moving back and forth. SPs provide the opportunity to beat the diffraction limit and confine light to very small dimensions. Under specific conditions, the incident light couples with the SPs to create self-sustaining, propagating electromagnetic waves known as surface plasmon polaritons(SPPs). However, the inherent metal loss makes it impractical to transfer digital data across the entire photonic circuits chip solely with plasmonic waveguides. Therefore, it becomes increasingly important to be able to integrate plasmonic modules with low-loss, dielectric optical interconnects and merge electronics and photonics on-chip at the nanoscale. To achieve such a goal, we propose to couple SPPs into the metal nanowires efficiently with an organic one-dimensional nanostructure in organic-noble metal heterojunctions, where organic nanowires can act as both low-loss waveguide and nanolaser. In this project, we will develop several methods to fabricate low-dimensional heterojunctions, including controllable movement of nanowires by micromanipulators, chemical synthesis of metal wire on organic wire surfaces and two-steps growth process in which preformed metal nanowires are used as seeds for the growth of vertically aligned organic nanowires. The photonic properties of obtained nanoheterojunctions will been investigated to reveal the dependence of launch efficiency, propagation loss and mode distribution of SPPs on the properties of incident light(frequency, polarization, phase, etc) and structural characterizations. The influence of metal nanowires on organic resonator will also been studied. Finally, a theoretical model will be built based on the careful analysis of experimental evidences, providing guidance for the rational design of SPP-based photonic devices.

不断增大的互连延迟以及热耗散等问题，已成为当前电子学发展面临的最大障碍。以光子为载体进行信息处理的光子学是克服瓶颈的最佳途径。然而，受限于衍射极限，光子回路的尺寸被限制在波长量级，很难实现光、电混合集成。金属为良导体，其纳米结构的表面等离激元（SPP）表现出来的奇异光学性质，为解决光、电集成回路中尺度不相容的难题带来新的契机。因此探索介质与金属界面的相关物理化学问题具有重要意义。 本项目从有机分子间弱相互作用出发，拟发展化学反应生长、液相自组装、气相外延生长等多种方法，构建有机-贵金属低维结构，研究界面处的激子过程，深入理解光子、激子与SPP的高效转化机制。结合材料结构特征分析其光子学性质，揭示入射光频率、偏振、相位等对介质材料激子行为、界面SPP的激励效率、SPP模式分布、传输损耗的影响以及SPP对纳米线谐振腔的作用机制，并通过理论模型验证，为理性设计基于SPP的光子学器件提供指导。

本项目按原计划顺利开展了相关研究工作，具体包括筛选了若干能量匹配的有机小分子化合物，研究分子的自组装行为及银纳米线的合成及提纯手段，在此基础上着重发展了液相共组装法，制备得到了形貌各异的有机-金属微纳复合材料。通过控制制备过程中的各种条件，制备出形貌可控，单分散性良好的掺杂微纳米异质结构，利用各种分析表征手段研究两种成分的形态及体系的能量传递及相关现象，探讨了纳米结构聚集体的组成、形貌和体系光电性质的关系，深入研究了有机材料组分间的激子能量转移过程以及激子与其他能量载体（如光子、表面等离子体）间的转化过程，解决了常规结构中表面等离激元激发效率低下的问题。并在此基础上设计构建了一系列光子元件，为实现集成光子回路奠定基础。四年来累计发表研究论文及综述7篇，其中影响因子大于10的文章6篇，影响因子大于4的文章1篇。