半导体量子点非线性光学性能研究
文献类型：学位论文
| 作者 | 李京周 |
| 文献子类 | 博士 |
| 导师 | 张龙 |
| 关键词 | 量子点 Quantum dots 非线性光学 Nonlinear optics 双光子吸收与发射 Two-photon absorption and emission 饱和吸收 Saturable absorption |
| 其他题名 | Nonlinear Optical Studies on Semiconductor Quantum Dots |
| 英文摘要 | 量子点是拥有几个纳米尺寸大小的半导体材料的原子团簇体，又称半导体纳米晶。因其独特的量子化能级结构，优异的光学可调性，超宽的增益与吸收，高光稳定性等独特的优点，使其在光电子器件、生物医学成像等方面存在众多应用。然而目前对量子点光学性能的研究还主要是集中在线性光学领域，对其非线性光学领域基本概念的阐述与实际应用仍然存在众多的盲区。本论文中，以胶体量子点为研究对象，通过实验与理论详细地阐述了CdTe/CdS及铅卤钙钛矿量子点的双光子性能与超快饱和吸收性能，具体包括以下几个部分： 1）CdTe/CdS量子点的超快饱和吸收性能研究。在本工作中，我们显示CdTe/CdS量子点具有优异的饱和吸收性能。在相同激发条件下，CdTe/CdS量子点分散液展现出比石墨烯更好的饱和吸收响应，与二硫化钼相当。在我们工作中也首次展示了量子点共振饱和吸收与非共振饱和吸收下的电子跃迁-弛豫过程。同时实验结果显示，量子点的限域效应可以有效调节量子点的双光子吸收性能，但是对量子点的饱和吸收性能无影响。进一步，基于CdTe/CdS量子点作为饱和吸收体，成功的实现了量子点的调Q激光输出。本工作中直接验证了量子点作为饱和吸收体的潜质，为进一步拓宽量子点在光电子方面的应用提供了实验与理论基础。 2）铅卤钙钛矿量子点非线性光学性能研究。本工作中，我们发现铅卤钙钛矿量子点有强的双光子吸收响应，其双光子吸收响应是传统硫系量子点的几倍。有趣的是，本工作中第一次在功率依赖荧光中观察到一个有卤素空位导致的高能缺陷峰。同时在本部分中我们也详细的阐述了钙钛矿量子点的饱和吸收特性，并通过其作为饱和吸收体成功的实现了蓝光调Q激光实验。 3）量子点-硅凝胶复合样品的双光子吸收、发射、及荧光猝灭机制研究。在本工作中，我们呈现了一个具有优异双光子性能的三维量子点-硅凝胶复合样品。溶胶-凝胶技术被引进用于耦合量子点进硅凝胶中。复合样品的双光子吸收、发射、载流子动力学性能被系统的研究。发现制备的复合样品的双光子性能综合优于稀土基掺杂的玻璃、陶瓷样品。特别的是，在我们的实验中引入动态成分分析方法解析量子点的高温荧光猝灭机制。发现荧光猝灭分为两个不同的区间，在最初的猝灭过程主要归于高温导致晶格内原子缺陷引起的。随着温度的增加，发现量子点的表面配体由于剧烈热涨落过程存在脱落，引起大量的表面缺陷生成。 综上所述，本文从实验到理论方面系统证实了CdTe/CdS量子点与铅卤钙钛矿量子点拥有优异双光子性能与饱和吸收性能，也进一步通过调Q实验验证了其作为饱和吸收体的可行性。同时，通过溶胶-凝胶技术耦合量子点进无机块体材料中的研究也为量子点的稳定应用提供了一种全新的技术路径。通过本工作，相信可以为胶体量子点在光子器件方面的应用打开另一扇窗户，丰富人们对胶体量子点的进一步认识。; Quantum dots (QDs), also referred to as semiconductor nanocrystals, are tiny clusters of semiconductor material with dimensions of only a few nanometers. Quantum dots have been widely used in some fields due to their quantized discrete energy structure, well-known fabrication methos, broad absorption, narrow emission, and size-tunable bang gap over a wide range of energy. However, for a long time, most of the studies were focused on the linear optical region of QDs. There are still many blind spots on the nonlinear optiacal properties and application of QDs. In this work, the two-photon properties and ultrafast saturable absorption properties of the QDs (CdTe/CdS and lead halide perovskite quantum dots) were systematically studied by experiments and theories. The contents of this thesis are shown as follows: 1) Ultrafast Saturable Absorption (SA) of the CdTe/CdS Colloidal Quantum Dots. In this work, we show the CdTe/CdS QDs have excellent SA performances by using an open-aperture Z-scan technique. More surprisingly, such QDs dispersions show better SA response than the current famous two-dimensional nanomaterials molybdenum disulfide and graphene dispersions. Our experiments directly reveal, for the first time, the electron excitation-relaxation processes of the resonant and non-resonant SA response of the QDs. And, we have also found that the quantum confinement effect of the QDs can regulate the two-photon absorption but does not affect the non-resonant SA performance. Further, based on the QDs as a saturable absorber, a superior passive Q-switching behavior in a laser cavity was observed. 2) Nonlinear optiacal properties of the cesium lead halide perovskite quantum dots. We found that, the perovskite QDs show several times higher two-photon absorption (TPA) response than that of the typical TP metal chalcogenide QDs. We also studied the excitation power-dependent TP PL optical properties systematically. More importantly, the emission peak induced by the high energy defect states of the halogen vacancy was observed experimentally for the first time. Furthermore, the SA properties of the perovskite QDs were also clarified. And, a superior passive Q-switching behavior in a laser cavity was observed using the perovskite QDs as a saturable absorber. It is suggested that the perovskite QDs would open up enormous research and development opportunities in the fields of nonlinear optics and material science. 3) Colloidal quantum-dot-based silica gel glass: two-photon absorption, emission, and quenching mechanism. We presented a three-dimensional quantum-dot-based solid matrix – a potentially excellent nonlinear material. The TP absorption, emission and carrier dynamic process of such material were systematically studied by open-aperture Z-scan and time-resolved fluorescence techniques. We found that such solid matrices have excellent two-photon (TP) properties, even better than the traditional nonlinear materials rare-earth-doped glasses and ceramics. More importantly, our work clearly clarified the mechanism for thermal quenching of the colloidal quantum dots (CQDs) by monitoring the change of the composition. We illustrated that the TP photoluminescence quenching generated firstly through the formation of the lattice defects. And, with further increasing of temperature, the surface ligands of the CQDs will fall off due to more violent molecules thermal fluctuations, which caused the produce of substantial surface defects. In summary, we confirmed that the CdTe/CdS and lead halide perovskite quantum dots have excellent two-photon properties and SA properties by the experiments and theories. Further, the feasibility of the QDs as a saturable absorber is also verified by a passive Q-switching experiment. At the same time, the research on the coupling of quantum dots into inorganic bulk materials by sol-gel technology provides a new way for the stable application of quantum dots. We believe that it will open up a new window for the application of colloidal quantum dots in photonic devices. |
| 学科主题 | 材料学 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/30965]  |
| 专题 | 中国科学院上海光学精密机械研究所 |
| 作者单位 | 中国科学院上海光学精密机械研究所 |
| 推荐引用方式 GB/T 7714 | 李京周. 半导体量子点非线性光学性能研究[D]. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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