量子点与贵金属纳米线阵列表面等离激元共振腔的耦合及单光子传输

Single-photon sources are a major challenge in quantum communication, quantum information processing, and quantum cryptography, wherein, the development of the single-photon sources based on cavities coupled with quantum dots is a research frontier, however, highly efficient emission and propagation at long distance of single photons at room temperature and under small mode volumes are still big problems. In this program, the emission and the propagation of single surface plasmons (i.e. single photons) will be presented by construction of coupling structures consisting of quantum dots and resonators of noble metal nanowire arrays. To prevent from the emission quenching, control of the dielectric layers between the resonators of noble metal nanowire arrays and the quantum dots will be investigated. Moreover, to avoid the interference from the coupling between the quantum dots and surface plasmons at other positons along the nanowires, the located assembly of the quantum dots at the end of the nanowire array resonators will be developed. On the other hand, the propagation losses of surface plasmons dependent on the parameters of structures and interfaces of the resonators, including diameter, spacing and length of the nanowires as well as the thickness of the dielectric layer, will be explored, the interface parameters dependence of the exciton-plasmon coupling in the quantum dots and the resonators will also be presented. In addition, the spontaneous emission rate of the resonators capturing the quantum dots can be remarkably increased and the propagation losses of surface plasmons can be significantly decreased by optimizing the interfaces, as a result, the highly efficient emission and propagation at long distance of single photons at room temperature and under small mode volumes can be achieved. This investigation will provide a new principle and method for realization of single-photon sources at room temperature as well as their applications in the quantum information field.

量子通信、量子信息处理和量子密码技术中富有挑战性的关键问题是单光子源。发展耦合量子点的腔体实现单光子源是研究前沿，然而在室温、小模式体积下实现单光子高效发射和长距离传输是当前面临的难题。本项目拟构筑量子点与贵金属纳米线阵列共振腔的耦合结构在室温下实现单个表面等离激元（单光子）的发射和传输。研究如何控制贵金属纳米线阵列共振腔与量子点之间的电介质层以阻止荧光淬灭，发展量子点在共振腔端部定位组装方法以避免其它位置量子点与表面等离激元耦合的干扰。探索共振腔结构界面参数（纳米线直径、间距、长度和电介质层厚度）对表面等离激元传输损耗的影响，探索量子点与共振腔耦合界面参数对激子与表面等离激元耦合的影响，通过优化界面大大提高共振腔捕获量子点发射光子的效率并降低传输损耗，进而在室温下实现单光子高效发射且在很小模式体积进行长距离传输。本项目研究将为构筑室温下的单光子源及其在量子信息中的应用提供新的原理和方法。

表面等离激元共振腔能突破光衍射极限的限制而展现极小的模式体积（纳米空间），且它能在室温下实现对光子的操纵以及光与物质的强相互作用，基于贵金属纳米结构的等离激元共振腔与光发射体的耦合将用于在室温下实现单光子源。本项目主要围绕贵金属纳米棒（或纳米线（长径比大于10的纳米棒即为纳米线））阵列等离激元共振腔与有源介质（荧光染料和量子点）的耦合结构制备和增强激光、荧光发射开展研究工作。主要研究内容、重要结果和关键数据包括：一是制备贵金属纳米棒（线）阵列的等离激元共振腔，通过改变纳米棒（线）长度对等离激元共振腔的模式特别是高阶谐波模式实现调控，研究贵金属纳米棒（线）表面等离激元模式激发，揭示不同模式其偏振依赖机理和实现在偏振器件中的应用，研究周期性金属纳米线阵列偏振性能和周期性光子晶体共振微腔的光学非线性效应并揭示了其物理机制；二是研究通过贵金属纳米结构表面等离激元强的局域电场与倾斜光纤光栅耦合来增强其包层模倏失场（增强光谱）进而提高传感性能；三是研究有源介质光发射体的荧光发射和激光模式调控，通过构筑不同有源介质体系探索光发射性能及其影响因素和机理，实现了低的激光阈值和对发射波长的调控；四是制备贵金属纳米棒（线）等离激元共振腔与有源介质的耦合结构，在室温下通过等离激元共振腔的模式调控有源介质的荧光发射，调控等离激元共振腔与有源介质之间的电介质层PMMA的厚度找到了阻止荧光淬灭、增强荧光效率的尺度参数，实现等离激元模式与有源介质荧光发射的光谱重叠并增强荧光发射和单光子激发。通过本项目研究为构筑等离激元共振腔与光发射体的强耦合体系及其在增强光谱方面的应用奠定基础，同时在室温下实现单光子（单个表面等离激元）发射将在量子信息中的应用提供原理和技术支撑。