等离激元红外吸收器及表面增强红外吸收光谱的研究

发布时间：2019-06-22 17:58

【摘要】：由于等离激元纳米结构对光的亚波长调控能力,等离激元在过去的二十年间受到广泛的关注。表面等离激元是一种局域于金属表面的电磁场与自由电子的耦合模式,发生于金属和介质分界面。利用等离激元模式,人们可以在纳米尺度实现光场的传导,聚焦与增强,为此在微纳光学器件与传感器领域有着广泛的应用。同时,利用金属表面的微结构可影响等离激元震荡的性质,为此过去的二十年间,如何通过金属纳米结构的设计与加工实现理想的纳米光学性质,实现光在纳米尺度调控一直被人们关注。近年来,研究人员在等离激元纳米结构以及能量的吸收过程方面进行了大量的研究。基于等离激元的红外吸收器,特别是在近红外和中红外的吸收器,由于它在生物传感、热成像、医疗诊断方面的广泛应用,引起了人们极大的兴趣。过去几年里,大量的纳米结构被应用到等离激元吸收器的设计上,例如光栅结构、纳米颗粒以及金属-介质-金属结构等。但是,这些结构多数只有一个等离激元共振峰,以及较低的吸收效率(50%)。因此,在本论文中我们设计了一个多共振吸收峰的等离激元超薄吸收器,并尝试用这个吸收器研究分子的表面增强红外吸收光谱。本论文研究的内容和结果如下：(1)设计了一个基于等离激元纳米谐振腔阵列的超薄红外吸收器,利用谐振腔极高的局域电磁场增强特性,从而达到对入射光的完美吸收。利用时域有限差分法对纳米谐振腔阵列进行数值模拟,发现吸收器的吸收峰随着谐振腔长度的增加而出现红移。为了得到多个连续变化的吸收峰,我们设计一个由15个等离激元纳米谐振腔阵列组成的吸收器。(2)利用电子束曝光技术,我们成功的制备了这个等离激元吸收器,并且深入的研究了电子束曝光工艺,包括曝光、显影、镀膜、剥离等过程。在制备的过程中,我们克服了曝光中的临近效应以及剥离失败的问题。(3)用傅里叶转换红外光谱仪对样品进行测量,获得了样品的红外吸收光谱。结果发现,制备的等离激元红外吸收器具有15个连续变化的吸收峰,和我模拟的结果相同。通过最小二乘法进行数据拟合,我们发现了吸收峰位置与谐振腔长度之间的线性关系方程,这对于设计特定波长的吸收器具有重要意义。(4)我们利用设计的等离激元红外吸收器较强的电磁场增强特性,来研究烯丙基硫醇分子的表面增强红外吸收光谱。由于修饰的巯基分子较少并没有探测到吸收增强的信号,但是我们以后还可以通过提高吸收器的吸收率以及更换修饰分子来继续研究表面增强红外吸收现象。我们这方面的工作,为以后进一步研究表面增强红外吸收以及表面增强拉曼散射奠定了基础。
[Abstract]:Due to the ability of isoionized exciton nanostructures to regulate the subwavelength of light, isoexciton has received extensive attention in the past two decades. Surface isolator is a coupling mode of electromagnetic field and free electron localized on metal surface, which occurs at the interface between metal and medium. By using the equal exciton mode, the conduction, focusing and enhancement of the light field can be realized at the nanometer scale, so it has been widely used in the field of micro-nano optical devices and sensors. At the same time, the microstructure of metal surface can affect the properties of isobaric oscillations. In the past two decades, how to realize the ideal nano-optical properties through the design and processing of metal nanostructures, and how to realize the control of light at the nanometer scale have been paid more and more attention. In recent years, researchers have done a lot of research on isoexciton nanostructures and energy absorption processes. The infrared absorber based on isobaric exciton, especially in near infrared and middle infrared, has attracted great interest because of its wide application in biosensor, thermal imaging and medical diagnosis. In the past few years, a large number of nanostructures have been applied to the design of isolator absorbers, such as grating structure, nanoparticles and metal-dielectric-metal structures. However, most of these structures have only one equal exciton resonance peak and lower absorption efficiency (50%). Therefore, in this paper, we design an isolator ultra-thin absorber with multiple resonance absorption peaks, and try to use this absorber to study the surface enhanced infrared absorption spectra of molecules. The contents and results of this paper are as follows: (1) an ultra-thin infrared absorber based on equal exciter nanoresonator array is designed, which makes use of the extremely high local electromagnetic field enhancement characteristics of the resonator to achieve the perfect absorption of incident light. The finite-difference time-domain method is used to simulate the nanoresonator array. It is found that the absorption peak of the absorber shifts red with the increase of the cavity length. In order to obtain several continuously changing absorption peaks, we design an absorber composed of 15 isoionized exciter nanoresonator arrays. (2) by using electron beam exposure technology, we successfully fabricated the isobaric absorber, and deeply studied the electron beam exposure process, including exposure, development, coating, peeling and so on. In the process of preparation, we overcome the proximity effect in exposure and the problem of peeling failure. (3) the infrared absorption spectrum of the sample was obtained by Fourier transform infrared spectrometer. The results show that the isoexciton infrared absorber has 15 continuously varying absorption peaks, which is the same as that of my simulation. Through the data fitting of the least square method, we find the linear relationship equation between the position of the absorption peak and the length of the resonator, which is of great significance for the design of the absorber at a specific wavelength. (4) We use the strong electromagnetic field enhancement characteristics of the designed isoexciter infrared absorber to study the surface enhanced infrared absorption spectrum of allyl mercaptan molecules. Because there are few modified sulfhydryl molecules, there is no signal of enhanced absorption, but we can continue to study the phenomenon of surface enhanced infrared absorption by improving the absorptivity of the absorber and replacing the modified molecules in the future. Our work in this field lays a foundation for further study of surface enhanced infrared absorption and surface enhanced Raman scattering.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB383.1

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