【作者】 张蕾；

【导师】 张汉壮； 张宇；

【作者基本信息】 吉林大学 ， 光学， 2014， 博士

【摘要】 胶体量子点材料是近几年来科研工作者们所关注的热点材料。因为与相应的体材料相比，它具有更为优异的电学和光学性质。例如：具有较宽的吸收光谱、较窄的发射光谱、较高的量子产额、较好的光学稳定性等。另外，由于量子限域效应，量子点吸收和发光光谱具有很强的尺寸依赖特性。而在众多的量子点材料中，PbSe量子点由于具有较大的玻尔半径（大约是46nm）、较强的量子限域效应和较宽的辐射范围等优异性质，从而获得越来越多的关注。另外，光纤在光纤通信方面，具有容量大，衰减小，体积小和防干扰性能好等优点；在光纤传感方面具有结构紧凑、灵敏度高等优点，从而受到广泛关注。本论文就将PbSe量子点和光纤结合起来，成功的制作成了PbSe量子点液芯光纤。研究PbSe量子点的荧光在光纤中传导后的输出光谱特性，我们叫做导向的自发辐射（guided spontaneous emission，简称GSE）。包括在光纤参数以及外界温度变化下的光谱特征。理论上建立了模型，在三能级系统近似下，得到了光在光纤中的功率演化方程，利用数值模拟方法得到了与实验数据相一致的结果，这为实验结果提供了一定的理论支持。最后，研究了在外界温度变化情况下的GSE光谱性质。这些研究在光纤通信方面、光纤放大器以及光纤传感器的研制方面具有一定的应用前景。论文主要内容如下：一、我们采用胶体化学法合成了不同尺寸的胶体PbSe量子点，并进行了TEM，XRD表征，其荧光量子产额可以达到89%。最后我们测量了不同尺寸的量子点的吸收（absorption，简称A b s）光谱以及发光（photoluminescence，简称PL）光谱，证实了量子点的禁带宽度是尺寸依赖的。二、我们将PbSe量子点中光的吸收与辐射过程近似为一个三能级系统，通过三能级系统的速率方程和光在光纤中的传播方程，建立了理论模型。模拟计算了在不同光纤参数影响下的光谱特征，这些参数包括光纤长度、光纤直径、量子点掺杂浓度和泵浦功率。最为重要的是，我们在模拟计算中考虑到了多种因素的影响，例如非辐射的俄歇复合、量子点的发光效率、光纤的模式泄露等。最后将理论结果与法国Hreibi小组的实验结果进行对比，得到了很好的一致，证明了我们理论模型的实用性。三、我们开展了对1.55μm通信窗口的量子点液芯光纤的研究。为此我们选用了尺寸为4.5nm的PbSe量子点。将合成好的PbSe量子点溶液灌装到空芯光纤中，封好。设计了实验方法并搭建光路，测试了在不同光纤参数影响下的GSE光谱，这些参数包括光纤长度、量子点掺杂浓度以及泵浦功率。另外，我们还对比了同样的PbSe量子点分别溶于甲苯和四氯乙烯溶剂中，做成的液芯光纤的GSE光谱的不同性质，详细分析了造成这种结果的主要原因。最后利用第四章建立的理论模型进行了理论模拟，与实验符合得很好。四、我们研究了两种尺寸的PbSe量子点液芯光纤在外界温度变化情况下的GSE光谱特征。包括光谱的峰值位置和峰值强度对温度的变化情况。最后从理论和实验的角度分析了产生这种现象的原因。这项研究在光纤温度传感器的研制方面具有一定的应用价值。更多还原

【Abstract】 Colloidal PbSe quantum dot is a hot material of scientific research workers inrecent years just because it has unique electrical and optical properties comparedwith the corresponding bulk materials. For example, they have relatively broadabsorption spectrum, narrow emission spectrum, high photoluminescence quantumyield (PL QY) and well optical stability. What’s more, the absorption andphotoluminescence (PL) of QDs present strong size dependent properties due tothe quantum confinement effect. Among many types of QDs, PbSe QDs have beengaining increased attention because of PbSe’s large Bohr radius (about46nm),strong size confinement effect, and tunable emission range. In addition, in opticalfiber communication, the fiber has many advantages such as large capacity, smallfiber loss, small volume and good anti jamming performance; in the aspect ofoptical fiber sensing, the fiber has advantages of compact structure and highsensitivity. So the fiber attracted much attention. This paper combined PbSe QDsand fiber, and made into PbSe QDs liquid-core fiber successfully. Studied thespectral (we called the GSE spectra (guided spontaneous emission)) properties ofthe PL of PbSe QDs after transmitted through the fiber. Included the spectralproperties when the fiber parameters and the temperature changes. Under the threelevel system approximation, we established the theoretical model and obtained theevolution equation of the optical power in the fiber. The result is consistent withthe experimental data which provides certain theoretical support for the experiment.Finally, the temperature depended GSE properties were studies in detail. Theresearch has a certain application perspective in the aspect of fiber communications,fiber amplifiers and fiber sensors. Our main work is arranged as follows.1. a series of PbSe QDs with different size was synthesized using colloidalchemical synthesis method. The PL QY can reach to89%. The absorption (Abs) and photoluminescence (PL) spectra were recorded for different size QDs. Theband gap of PbSe QDs were approved to be size depended.2. the absorption and emission in the PbSe QDs can be approximated to be athree level system. The theory model was established through solving the rateequations and the power propagation equations in the fiber. Simulated theproperties of the spectra under the influence of fiber parameters, included the fiberlength, the fiber diameter, the doping concentration and the pump power. Moreimportantly, many influence factors were considered in our simulations. Such asnon-radiative transition (Auger recombination), luminescence efficiency of PbSeQDs and the mode leakage of the fiber and so on. F inally, our theoretical resultswere compared with the experimental data reported by Hreibi, et al. and wereproved to be a good practicability.3. PbSe QD-doped liquid-core fiber worked in the1.55μm communicationwindow was studied. The PbSe QD solution with diameter of4.5nm were filledinto hollow core fiber and sealed up seriously. After that, we designed theexperimental method, set up the light path and recorded the GSE spectra underdifferent fiber parameters, including fiber length, doping concentration and pumppower. In addition, we compared the influence of the two solvent to the propertiesof the GSE spectra and explained the reasons for the phenomenon in detail. In thelast, the theory result was obtained using the theory model in chapter4and fittedwell with the experimental data.4. the GSE properties of PbSe QD-doped liquid-core fiber under theinfluence of the temperature for the two QD size was studied. We focused on thechange of the peak position and peak intensity of the spectra when the temperatureincreased. Finally, the reasons of the experimental phenomena were analysized bytheory. This study has a certain application value in the fiber temperature sensor.更多还原