二维半导体超快非线性光学性质研究
文献类型：学位论文
| 作者 | 王康鹏 |
| 学位类别 | 博士 |
| 答辩日期 | 2014 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 张龙 |
| 关键词 | 非线性光学 二维半导体材料 Z扫描 过渡金属硫系化合物 碲 |
| 其他题名 | Ultrafast Nonlinear Optical Studies on Two-dimensional Semiconductors |
| 中文摘要 | 二维半导体材料由于量子限制效应和层间微扰的缺失，相对于其对应三维材料表现出独特的物理、机械和电子学性质，成为当前研究的热点。由于下一代电子器件需求的紧迫性和电子工业方面应用的驱动，目前关于二维半导体材料的研究主要围绕其电子学和光子学性质，探索其作为半导体场效应管、光探测器、发光LED等方面的应用潜力。而对二维半导体作为纳米光子学器件如全光开关、超快锁模器件等方面的应用潜力的认识尚处起步阶段，因而其非线性光学性质的方面的研究则报导较少。本论文中，我们结合对新一代纳米光子学材料的应用需求的背景，对二维半导体材料的非线性光学展开了一些前沿探索性的研究，具体包括以下几个部分： 1. 非线性光学表征平台的搭建。 Z扫描技术是一种基于单光束的非线性光学测试方法。为了能够简便、迅速的分析样品的非线性光学性质，我们从零起步先后建立两套Z扫描系统并为其编写控制软件。两套系统基于不同的硬件架构（功率计和数据采集卡），控制的软件也分别用Visual Basic 6.0和Labview编写，最终的系统经过测试，满足了预先设定的要求。特别是基于数据采集卡和Labview的Z扫描系统，操作方便、功能齐全、运行稳定。另外，为了加快Z扫描数据的分析，利用Matlab编写了一套Z扫描数据拟合软件。该软件集成了常用的非线性模型，能够拟合开孔、闭孔的Z扫描数据，快速获得样品的非线性参数。 2. MoS2二维半导体纳米片的超快非线性响应研究。 基于超声液相剥离技术，我们成功的制备了含有大量MoS2二维纳米片的高品质分散液并对其进行了微观结构表征和光谱表征。表征结果表明了分散液中含有大量高质量、少缺陷的二维MoS2纳米结构。为了研究样品的超快非线性响应，我们利用800 nm飞秒激光对样品进行了开孔Z扫描测试。结果表明了MoS2二维半导体纳米片具有优异的饱和吸收性质，并且其性能超过了对应的石墨烯分散液。上述结果证实了以MoS2二维半导体纳米片在纳米光子器件方面较大的应用潜力。 3. 钼硫系化合物二维半导体纳米片的宽带非线性响应研究。 基于研究MoS2二维半导体纳米片的超快非线性响应的基础，我们将二维半导体材料的非线性光子学研究拓展到其他钼硫系化合物。利用多种激光和开孔、闭孔Z扫描系统，我们系统的研究了钼的硫系二维半导体纳米片分散液从可见到近红外频域、从皮秒到飞秒时域的非线性吸收和非线性折射。我们发现所有的钼硫系化合物二维半导体纳米片分散液对于文中所用激光呈现明显的饱和吸收响应，这些响应可以占主导地位的多层纳米片来解释。为了证实这个观点，我们提高样品制备时的离心速度（相应的纳米片平均层数减少），发现MoS2和MoSe2分散液在1030 nm的飞秒脉冲作用下转变为双光子吸收过程。实验过程中，我们还观察到分散液对皮秒激光的自散焦效应，这种现象来自于分散液吸收激光能量所产生的热致折射率改变。研究证实了钼硫系化合物优异的非线性光学性质。 4. 生物合成Te纳米颗粒及其共轭复合物的非线性响应研究。 生物合成纳米材料由于其低成本、环境友好的优点引起人们的普遍关注。我们利用厌氧细菌Bacillus selenitireducens的代谢作用合成大量的Te(0)纳米颗粒。通过与共轭聚合物PmPV的甲苯溶液复合得到稳定的Te(0)/PmPV复合物。利用800 nm飞秒激光、532/1064 nm纳秒激光对复合物进行了Z扫描实验，研究其在不同频域、时域激光下的响应，并对其机理作出解释。同时，我们还比较了生物合成Te样品和化学合成Te样品的非线性响应的差别。我们的研究结果表明了生物合成的Te(0)纳米颗粒在纳米光子学领域广阔的应用前景。 5. 光在具有两种不同非线性机理的级联非线性介质中的传播规律。 多种非线性介质在单一器件中的结合是未来设计非线性光子学器件发展的方向。为了研究光在多种非线性光学介质中的传输过程和规律，我们设计了碳纳米管分散液和酞菁溶液组成的级联非线性介质。应用Z扫描技术，我们得到了非线性级联介质在高斯光束作用下的非线性响应。进一步的，利用Matlab计算环境，我们用数值计算的方法对光在介质中的传输过程进行了模拟。模拟结果与实验过程中得到非对称Z扫描数据非常吻合。我们的结果和研究方法对设计包含多种非线性介质的非线性器件有重要意义。 |
| 英文摘要 | Recently, significant effort has been devoted to the study of two-dimensional van der Waals semiconductors because their remarkable physical, mechanical and electronic properties due to the lack of quantum confinements and interlayer disturbances comparing to their bulk counterparts. With the driven of electronic and semiconductor industry, great attentions are recently attracted by the research on the electrical and opt electrical properties of two-dimensional semiconductors in order to reveal their potentials as the fundamental materials of next generation digital electronic devices. Several groups have reported the emerging applications of 2D semiconductors as field-effect transistor (FET), RF component, photodetector, solar cell and light emitting diode (LED). Despite the intense research on the electronic properties, the nonlinear optical (NLO) properties of 2D semiconductors and their potential applications in nanophotonics are still far from revealed. In this thesis, we carried out a series of the frontier investigations on the NLO response of 2D semiconductors with the purpose of application in NLO devices. The contents of this thesis are shown as follows: We started our work with the build of NLO measurement devices. With the purpose to be simply and fast to collect the NLO data, we built up two Z-scan systems and compiled two pieces of control software independently. The two Z-scan systems based on different framework, i.e., powermeter and high-speed digitalizer respectively. The control software were developed in Visual Basic 6.0 and Labview 2010 respectively. The reliability of the Z-scan systems were tested with standard samples. It should be mentioned that the Z-scan system with high-speed digitalizer possess the features of high accuracy and stability, and ability to measure open- and closed aperture simultaneously. In addition, to speed up the analysis of Z-scan data, one piece of software was designed for Z-scan curve fitting by Matlab. A series of NLO models were integrated including nonlinear absorption and nonlinear refraction. These works were the fundamentals for the rest in this thesis. After building the reliable Z-scan setup, we conducted the investigation on NLO properties of MoS2 2D semiconductors. Employing high-yield liquid phase exfoliation (LPE) technique, we prepared a series of dispersion containing a large quantity of high quality pristine 2D MoS2 nanostructures, which was verified by transmission electron microscope (TEM), UV-Vis and Raman characterization. In order to determine the ultrafast NLO response of MoS2 dispersions, 800 nm femtosecond laser was incorporated to the open aperture Z-scan. The results showed the significant saturable absorption response of MoS2 2D semiconductor nanosheets exceed that of graphene, implied the promising potentials of MoS2 2D semiconductor in nanophotonic device. Based on the ultrafast NLO research of MoS2, we extend the NLO investigation to the other 2D molybdenum dichalcogenide semiconductors, i.e., MoSe2 and MoTe2. By introducing a series of laser from visible to infrared and picosecond to femtosecond to open- and closed aperture Z-scan, the NLO absorption and refraction of molybdenum dichalcogenide dispersions were systematically investigated. It was found out that all the dispersions exhibited obvious saturable absorption with the excitation of all the laser mentioned in the context, which could be explained by the domination of few-layer nanosheets. In order to reveal the relationship between number of layer and the NLO response, another batch of dispersions were prepared by same method except higher centrifugation speed. With 1030 nm femtosecond irradiation, two-photon absorption instead of saturable absorption was observed in MoS2 and MoSe2 dispersions with high centrifugation speed. Furthermore, we observed self-defocusing effects in all the dispersions, which was caused by thermal induced refraction index change. Our work verified the promising NLO properties of 2D molybdenum dichalcogenide semiconductors. The biological synthesized nanostructures attracted great attention because their inherent low cost and environment friendly benefits. In our work, elemental tellurium nanostructures were prepared via an environmentally friendly microbiological synthesis technique, respiration of anaerobic bacterium Bacillus Selenitireducens. The collected Te(0) were dispersed in a π-electron-riched conjugated polymer PmPV, forming a bio-nanocomposite. Open-aperture Z-scan studies reveal that Te(0) shows strong saturable absorption for 100 fs pulses at 800 nm and Mie scattering induced extinction effect for ns pulses at both 532 nm and 1064 nm. The low-cost microbiologically synthesized Te(0) possesses an equivalent NLO performance to the chemically synthesized Te(0). The various NLO responses of Te(0) implies the high potentials in applications as mode-locking etc. The understanding and simulation of high-power laser propagation and energy transport in multi-layer mediums drive the development of NLO devices applied in communication, material processing, medical devices, etc. In this work, laser propagation (532nm, 6ns) in two-layer media with different NLE mechanism is studied by standard Z-scan method. A two-cell cascade cuvette is designed for this purpose, which filled with single-walled nanotube (SWNT) dispersions and zinc phthalocyanine (ZnPc) solutions separately. By changing the sequence of light passing through each material, the laser was attenuated with different velocity, resulting variant Z-scan results. After that, numerical simulations were conducted for understanding the distribution of laser intensity in medium. It should be mentioned that the asymmetric Z-scan curves obtained from experiments are well simulated by numerical calculation. Our work may help the development of NLO devices comprising multiple NLO mediums. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15883]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 王康鹏. 二维半导体超快非线性光学性质研究[D]. 中国科学院上海光学精密机械研究所. 2014. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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