表面等离激元共振诱导的金纳米结构的三阶光学非线性增强效应研究

发布时间：2018-12-15 06:02

【摘要】：表面等离激元由于具有局域场增强和高效耦合能量传输特性而被广泛研究。基于表面等离激元特性的金属纳米结构可应用于表面增强拉曼散射,超灵敏单分子探测、生物癌症治疗和纳光子器件等领域。贵金属复合纳米结构由于局域场增强和共振吸收而具有大的三阶光学非线性,其在光开关、光信息处理和光电子器件等领域的应用一直是等离激元学研究的重点。而金属纳米结构的超快时间响应特性也是等离激元学的一大研究热点。金属表面等离激元诱导的热电子在光电转换、光电探测、光化学反应、以及超快器件等方面有着重要的应用。因此更深入的理解热电子的产生和弛豫过程的物理机理,这对于热电子的应用来说是非常重要的前提,进而可通过调控纳米结构参数和激发条件来控制热电子的产生和弛豫时间尺度。本论文主要研究了表面等离激元共振增强的Au-Ni-Au复合纳米棒阵列的三阶光学非线性,金纳米锥的三阶光学非线性和超快时间响应特性,以及铝纳米薄膜结构的三阶光学非线性,并介绍了光路系统的搭建及其原理。主要内容包括以下几个方面： 1.我们搭建了光克尔、超连续白光泵浦探测和Z-scan光路,并对各个光路的理论、所测量的物理量和其内在物理机理进行了详细描述。并利用Z-scan和光克尔光路对金属纳米结构的三阶光学非线性和超快时间响应特性进行了研究。 2.我们在氧化铝模板中制备了直径为18m的Au-Ni-Au复合纳米棒阵列。该复合纳米棒的纵向等离共振波长大约在800nm处。利用Z-Scan技术测量了该样品的三阶光学非线性。在纵向等离共振波长处得到了大的三阶非线性吸收系数-2.65×106cm/GW。 Au-Ni-Au复合纳米棒的非线性吸收系数随激发波长和入射光角度的变化规律表明,三阶光学非线性的巨大增强是由于纳米棒间的纵向等离激元的强耦合作用导致的。通过比较Au-Ni-Au复合纳米棒阵列与纯Au单段纳米棒阵列,我们发现在第一段Au生长后,再沉积一层很薄的Ni,然后再生长一段Au将会导致三阶光学非线性的极大的增强。这可归因于纳米界面中的纳米捕获能级的形成和相邻棒之间及棒内多段之间的局域场增强的共同作用。这种纳米结构的设计和测量手段给人们提供了一种非常有效的方式来操控未来等离子光学器件中的非线性光学性质。 3.通过光克尔时间分辨技术,我们研究了金纳米锥的三阶非线性光学极化率和超快时间响应。随着激发光波长从非共振波长(780nm)移动到纵向共振波长(825nm)时,金纳米锥的三阶非线性光学极化率从7.4×10-14esu增加到3.9×10-13esu,其品质因子在～10-13esu.cm量级。金纳米锥的超快时间响应曲线呈现出两个不同的衰减过程,其快衰减过程从141±23fs到83±8fs,慢衰减过程从3200±200fs到2310±158fs。大的三阶非线性光学极化率的增强是由表面等离激元共振所引起的局域场增强导致的,快和慢衰减过程的响应时间的加快是由金纳米锥体系中表面等离激元共振引起电子与电子,电子与声子的散射几率的增加而导致的。这些基础研究提供我们一种控制热电子的时间尺度的方式,通过设计并制备合适的纳米结构,调节其等离共振峰来调控表面等离激元诱导的热电子的弛豫时间,从而应用于光催化、光探测和光捕获等方面。金纳米锥的超快光学性质使得其在未来的超快光信息处理领域也有着很大的应用价值。 4.我们对关于铝的表面等离激元的研究进行了介绍,并对铝的表面等离激元的特性、应用进行了详细的描述。基于铝的表面等离激元的优异特性,我们期望能通过调控基底的结构参数和镀膜条件来获得不同结构类型和尺寸的铝纳米薄膜,从而实现对铝的表面等离激元共振波长的调控并同时获得大的三阶光学非线性响应。因而我们通过模板电化学的方法制备了两种类型的氧化铝模板,并利用蒸镀法在氧化铝模板上蒸发形成了铝纳米孔洞膜,再利用Z-scan技术对其三阶光学非线性性质进行了测量。下一步的工作是研究氧化铝模板的结构参数和镀膜条件对铝的表面等离激元共振波长和其三级光学非线性性质的影响。将开展的研究工作为铝的表面等离激元的应用提供一种简单、易操控且可行性高的制备铝纳米结构的方法。
[Abstract]:The surface plasmon is widely studied due to the local field enhancement and high efficiency coupling energy transmission characteristics. The metal nanostructure based on the surface plasmon characteristics can be applied to the fields of surface enhanced Raman scattering, ultra-sensitive single-molecule detection, biological cancer treatment, and nano-photonic devices. The composite nano-structure of the noble metal has a large third-order optical nonlinearity due to the local field enhancement and the resonance absorption, and the application of the noble metal composite nano-structure in the fields of optical switches, optical information processing, and optoelectronic devices has been the main focus of the research on the plasmon excitation. The super-fast time-response characteristics of the metal nanostructures are also a hot topic in the study of the isotropy. It is an important application in the aspects of photoelectric conversion, photoelectric detection, photochemical reaction, and ultra-fast device. Therefore, it is very important to understand the generation of hot electrons and the physical mechanism of the relaxation process, which can control the generation and relaxation time scale of the hot electrons by controlling the nano-structure parameters and the excitation conditions. The third-order optical nonlinearity of the Au-Ni-Au composite nanorod array, such as the surface plasmon resonance enhancement, the third-order optical nonlinear and ultra-fast time response characteristics of the gold nano-cone, and the third-order optical nonlinearity of the aluminum nano-film structure, are studied in this paper. The construction and the principle of the optical path system are introduced. The main contents include the following aspects: 1. We set up the optical Kerr, the ultra-continuous white light pump detection and the Z-scan optical path, and the theory of each optical path, the measured physical quantity and the physical mechanism in it. The third-order optical nonlinear and super-fast time-response characteristics of the metal nanostructures were studied by using the Z-scan and the optical Kerr optical circuit.. 2. We prepared an Au-Ni-Au composite with a diameter of 18m in an alumina template. the longitudinal or the like of the composite nanorods is approximately 800 from the resonant wavelength, The third-order optical of the sample was measured using the Z-Scan technique. Non-linear. Large third-order non-linear absorption coefficient-2.65-106cm is obtained at the longitudinal and other off-resonance wavelengths. The variation of the nonlinear absorption coefficient of the Au-Ni-Au composite nanorods with the excitation wavelength and the incident light angle shows that the large enhancement of the third-order optical nonlinearity is due to the strong coupling effect of the longitudinal and other off-excitation elements between the nanorods. By comparing the Au-Ni-Au composite nanorod array and the pure Au single-segment nanorod array, we find that after the first segment of Au is grown, a very thin layer of Ni is deposited, and then the growth of a segment of Au will result in the third-order optical non-linearity. enhancement. this can be attributed to the formation of the nano-capture level in the nano-interface and the co-operation of the local field enhancement between the adjacent rods and the multi-segment in the rod, the design and measurement means of such nanostructures provide a very effective way to control non-linear light in a future plasma optical device, 3. The third order nonlinear optical polarization of the gold nano-cone is studied by the optical Kerr time resolution technique. The third-order nonlinear optical polarization of the gold nano-cone is increased from 7. 4 to 10 to 13 esu, and its quality factor is in the range of ~

10-13esu. cm 【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1

【相似文献】