基于共振激发下单个胶体量子点新颖光学效应的研究

Quantum fluorescence properties of single colloidal quantum dots have been recognized by measuring the anti-bunching effect, but the fluorescence blinking and spectral diffusion phenomena caused by Auger effect seriously shorten the decoherence time and obtaining a stable, highly efficient and coherent single photon sources has become the present difficulties in study. The program proposes that the resonance excitation of single CdSe colloidal quantum dots with greatly suppressed Auger effect in planar microcavity or micro-nano optical fiber surface can achieve single photon sources of high performance. The program mainly based on single molecule spectroscopy detection studies resonance fluorscence properties of single colloidal quantum dots with resonance excitation in planar microcavity or micro-nano fiber surface;analyzes the influence of spectal diffusion and coupling effects between exciton and phonon on coherent properties of single photon sources; sets up the correlation model between spectral diffusion and fluorescence blinking; explores the novel coherent optical properties of colloidal quantum dots with variable power excitation.The program can effectively eliminate the decoherence effects of reaxation mechanism and laser background noise, and can also effectively collect resonance fluorescence. Therefore, this program can provide a high quality single photon sources for quantum communication, and will also provide a new scientific means for the realization of quantum state manipulation of single photon in colloidal quantum dots.

单个胶体量子点的量子发光性质通过反聚束效应的测量得到确认，可是由于俄歇效应所导致的荧光闪烁和光谱漂移现象严重地缩短了去相干时间,如何得到稳定、高效、相干的单光子源成为目前研究的难点。本项目提出低温下共振激发在平面微腔内或微纳光纤表面的俄歇效应得到抑制的单个CdSe胶体量子点来获得高性能的单光子源。本项目主要基于单分子光谱技术的探测方法：(1)研究共振激发平面微腔内或微纳光纤表面的单个胶体量子点产生的共振荧光特性；（2）分析频谱漂移及激子和声子的耦合效应对单光子源相干性能的影响；（3）建立共振激发下频谱漂移与荧光闪烁的关系模型；（4）探索变功率共振激发下胶体量子点新奇相干光学特性。本项目既可以有效消除激光背景噪声及弛豫机制对激子退相干的影响，又可以有效收集共振荧光。因此，本项目的研究既可以为量子通信提供一种优质的单光子源，也将为在胶体量子点中实现单光子量子态的操纵提供一种新的科学技术手段。

通过单分子光谱技术，研究单个量子点的新颖光学特性: (1) 研究了单个石墨烯量子点的荧光光谱及激子动力学特性，发现在紫外激发区域具有量子受限效应，并建立了石墨烯量子点发光机制模型; (2) 实现了单个硒化镉胶体量子点与染料分子间的能量传递，并在单点尺度上证实了Forster能量转移动力学理论 ; (3) 实现了自组织量子点在平面微腔内激子与声子发生强耦合，并产生极强的上转换荧光效率; (4) 研究硒化镉胶体量子点内多激子效应，设计量子点中的量子态作为能量转移的给体，而捕获态作为能量转移给受体，通过增加激光激发功率多激子通过能量转移给捕获态实现了延时存储; (5) 研究通过拉制微纳光纤表面倏逝波共振激发单个胶体量子点，观察到常温和低温下共振激发下激子与声子耦合产生荧光上转换效应, 实验发现共振激发下单个胶体量子点的荧光闪烁现象得以有效抑制.