金属等离激元微结构的光俘获操纵和表面增强拉曼散射研究
发布时间：2018-08-18 13:13
【摘要】：亚波长金属微纳结构及其表面等离激元的激发、耦合和传播所引起的丰富的光学性质是当前能源科学、信息科学、材料科学及其交叉领域的研究热点之一。近年来,不断深入的理论研究伴随着纳米材料的精确加工和控制技术的飞速发展,针对不同应用领域的功能化新型金属等离激元微结构材料的设计层出不穷,为人们实现光子的操纵和光物质相互作用的调控提供了大量有效的解决方案,并在高效光电转换、光学非线性效应增强以及纳米集成光学芯片等领域展现出了极大的应用前景。本论文围绕如何利用等离激元微纳结构调控电磁波在介质中激发和传播这一科学问题,研究了利用人工金属微结构实现高效宽带光子俘获的机制和结构设计方案,并探索等离激元激发的光学吸收和局域场增强协同下的表面增强拉曼散射效应。论文主体的第一部分是理论设计并实验制备出一种基于二维无序胶体晶体的金属微纳结构,从而实现工作波长可调的超宽带、入射角及偏振不敏感的等离激元共振完美吸收器。在论文主体的第二部分,我们针对当前量子阱光电探测器在红外光耦合效率方面遇到的问题,利用杂化类表面等离激元共振模式和微腔模式的耦合效应,设计出一种针对多层量子阱工作在甚长波红外波段(14μm-16μm)的光耦合器,实现了光耦合效率的显著提高。在论文的第三部分,我们将纳米压印技术以及改进的纳米球刻印技术与金属纳米颗粒的沉积技术相结合,制备出了一系列大面积、高均匀性的金属纳米颗粒阵列结构,并探索其对于表面增强拉曼散射(SERS)效应的调控。论文主要研究内容包括以下几个方面:1、基于大面均匀无序二维胶体晶体的自组织技术,设计并制备了宽带等离激元-光子完美吸收结构。该结构是通过在平整金膜上无序排列二维胶体晶体,然后沉积不同厚度金膜层得到的,其全吸收性质来源于等离激元耦合的法布里-珀罗共振模式和磁等离激元腔模等模式的激发。由于布洛赫本征模式被无序点阵抑制,相比于有序结构体系无序排列的等离激元-光子吸收器能够产生更宽波段的完美吸收现象。为了更进一步的拓展带宽,我们把不同尺寸的胶体微球混合排列,利用几何尺寸对光吸收调控的影响,有效地实现了近红外波段超宽带的完美吸收。同时,由于单个共振单元的对称性以及系统无序的排列方式的特性,该近红外全吸收器展现出偏振无关和宽角度响应的特点。我们设计的体系是基于成熟的金属膜层沉积以及胶体晶体的自组装方法,具有制备工艺要求低、成本可控以及高重复性等优点,并且通过改变微球尺寸和金属膜厚度的改变,可以实现此超宽带全吸收器的工作波段在从可将光到红外全波段的调谐。2、量子阱红外探测器(QWIPs)相比以传统材料碲镉汞(HgCdTe)制备的红外探测器在制成大面积、低功耗、低成本、高均匀性和高灵敏度的焦平面列阵(FPA)成像系统方面具有显著优势。然而对于常用的n型QWIPs,由于子带间跃迁的选择定则,量子阱层对于垂直入射的电磁波不能耦合。论文提出了一种工作在甚长波红外波段针对于多层量子阱光电探测器高效的金属光学耦合结构,这种耦合结构支持杂化类表等离激元共振和微腔共振两只共振模式,通过调控这两种模式的耦合,有效地提高了量子阱活性区域光子态密度,特别是使得电场Ez分量获得了显著的增强,提高了 QWIPs的光耦合效率。我们设计的耦合结构相比于无金属微结构参考体系中量子阱活性层的吸收增强了 33倍左右,同时表征在量子阱活性层内电场Ez分布的耦合效率因子(η)达到了 6。另外,我们设计的金属微结构展现出了很大入射角度的适用性(入射角度可达40°)以及对入射偏振的不依赖性。依据数值模拟计算的论证,我们提出了结合分子束外延生长技术以及标准的光学刻印技术的高性能红外光电探测器聚焦平面阵列器件制备方案。3、基于纳米压印技术以及改进纳米球刻印技术,结合精确控制的金属纳米颗粒沉积技术制备了一系列大面积、高均匀性金属纳米颗粒阵列结构作为SERS衬底。首先我们提出并且制备了 一种基于氧化铝模板纳米压印技术和金属纳米颗粒沉积技术的金/PC纳米柱阵列组成的SERS衬底,通过调控AAO模板的结构参数和镀金厚度来调节金/PC纳米柱阵列的光学性质。由于局域等离激元耦合效应,在邻近金/PC纳米柱之间的超小间隙中获得了超高局域场增强,使得SERS效应有了明显的增强。这种金/PC纳米柱阵列实际上是处于有弹性的PC薄膜上,因此外力扭曲和拉伸等将为SERS提供另一种调节的自由度。其次,我们介绍了一种通过改进的纳米球刻印技术制备的有着大量亚纳米级超小间隙的准三维金属网SERS衬底。这种衬底具有高达1.5×108的拉曼增强因子,可以探测到的浓度低至1× 10-9M的水溶液中的R6G分子,在SERS强度随空间位置分布的测试中,相对标准偏差仅为10.5%,表现出极佳SERS均匀性。此外,我们基于相分离刻印技术在硅片上制备了大面积银颗粒阵列,这种阵列展现出了高均匀性且达到1.64×108的拉曼增强,除此之外,相对于传统的制备方法,通过相分离刻印技术制备SERS衬底方法简单、成本低廉,具有明显的产业应用前景。
[Abstract]:The abundant optical properties caused by the excitation, coupling and propagation of sub-wavelength metal Micro-Nanostructures and their surface plasmons are one of the hotspots in the fields of energy science, information science, material science and their cross-cutting. Designs of novel functional metal plasmon microstructures for different applications have emerged in an endless stream, providing a large number of effective solutions for the manipulation of photons and the regulation of light-matter interactions, and exhibiting high-efficiency photoelectric conversion, enhancement of optical nonlinear effects, and nano-integrated optical chips. Focusing on the scientific problem of how to modulate the excitation and propagation of electromagnetic waves in media by using plasmon microstructures, this paper studies the mechanism and structure design scheme of high-efficiency broadband photon capture using artificial metal microstructures, and explores the optical absorption and local field enhancement synergy of plasmon excitations. The first part of this paper is the theoretical design and experimental fabrication of a two-dimensional disordered colloidal crystal-based metal micro-nano structure, so as to achieve wavelength-tunable ultra-wideband, incident angle and polarization-insensitive plasmon resonance perfect absorber. Aiming at the problems of quantum well photodetectors in infrared optical coupling efficiency, a kind of optical coupler for multilayer quantum wells operating in very long wave infrared (14-16 micron) band was designed by using the coupling effect of hybrid surface plasmon resonance mode and microcavity mode. The optical coupling efficiency was greatly improved. In the third part of this paper, we combine nanoimprinting technology with improved nano-lithography technology and metal nanoparticle deposition technology to fabricate a series of metal nanoparticle arrays with large area and high homogeneity, and explore their regulation on surface-enhanced Raman scattering (SERS) effect. Based on the self-organization technique of large-plane homogeneous disordered two-dimensional colloidal crystals, a broadband plasmon-photon perfect absorption structure is designed and fabricated. The structure is obtained by disorderly arrangement of two-dimensional colloidal crystals on a flat gold film and deposition of different thickness of gold film. The total absorption properties of the structure are derived from plasma exciton coupling. The excitation of the combined Fabry-Perot resonance mode and the magnetic plasmon cavity mode can produce a wider band of perfect absorption than the disordered plasmon-photon absorber in the ordered structure system because the Bloch eigenmode is suppressed by the disordered lattice. The hybrid arrangement of colloidal microspheres utilizes the influence of geometrical size on the regulation of optical absorption to achieve the perfect absorption of near-infrared ultra-wideband effectively. At the same time, due to the symmetry of a single resonant unit and the disordered arrangement of the system, the near-infrared full absorber exhibits the characteristics of polarization-independent and wide-angle response. The designed system is based on mature metal film deposition and colloidal crystal self-assembly method. It has the advantages of low preparation process requirements, cost control and high repeatability. By changing the size of microspheres and the thickness of metal film, the ultra-wideband total absorber can be operated in the full band from light to infrared. 2. Quantum well infrared detectors (QWIPs) have significant advantages over conventional HgCdTe infrared detectors in fabricating large-area, low-power, low-cost, high-uniformity and high-sensitivity focal plane array (FPA) imaging systems. However, for n-type QWIPs, due to the selection of inter-band transitions, Quantum well layers can not be coupled to vertically incident electromagnetic waves. In this paper, an efficient metal optical coupling structure for multilayer quantum well photodetectors in very long wave infrared band is proposed. The coupling structure supports two resonant modes, hybrid surface plasmon resonance and microcavity resonance, by adjusting the two modes. Coupling effectively enhances the photon density of states in the active region of quantum wells, especially the Ez component of the electric field, and improves the optical coupling efficiency of QWIPs. The coupling efficiency factor (_) of the Ez distribution in the layers reaches 6. In addition, the metal microstructures we designed exhibit the applicability of large incident angles (up to 40 degrees) and the dependence on the incident polarization. Based on the numerical simulation, we propose a combination of molecular beam epitaxy and standard light. A series of large-area, highly homogeneous metal nanoparticle arrays have been fabricated as SERS substrates based on nanoimprinting and improved nano-ball lithography. Firstly, we introduce the fabrication of SERS substrates with high-performance infrared photodetectors. A SERS substrate consisting of gold/PC nano-column arrays based on alumina template nanoimprinting and metal nano-particle deposition techniques was prepared. The optical properties of gold/PC nano-column arrays were adjusted by adjusting the structural parameters and the thickness of gold plating on AAO template. This kind of gold/PC nano-column array is actually situated on the elastic PC film, so the external force distortion and stretching will provide another degree of freedom for SERS. Secondly, we introduce an improved nano-ball lithography technique. A quasi-three-dimensional metal mesh SERS substrate with a large number of sub-nanometer ultra-small gaps has been fabricated. The substrate has a Raman enhancement factor of 1.5 *108 and can detect R6G molecules in aqueous solutions with concentrations as low as 1 *10-9M. The relative standard deviation (RSD) of the SERS strength distribution with spatial position is only 10.5%, showing excellent SERS performance. In addition, we have fabricated a large area of silver particle arrays on silicon wafers based on phase separation lithography. The arrays exhibit high homogeneity and Raman enhancement of 1.64 *108. In addition, compared with traditional methods, the method of preparing SERS substrate by phase separation lithography is simple, low-cost and has obvious yield. Industry application prospects.
【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB383.1;TG111
本文编号：2189575
[Abstract]:The abundant optical properties caused by the excitation, coupling and propagation of sub-wavelength metal Micro-Nanostructures and their surface plasmons are one of the hotspots in the fields of energy science, information science, material science and their cross-cutting. Designs of novel functional metal plasmon microstructures for different applications have emerged in an endless stream, providing a large number of effective solutions for the manipulation of photons and the regulation of light-matter interactions, and exhibiting high-efficiency photoelectric conversion, enhancement of optical nonlinear effects, and nano-integrated optical chips. Focusing on the scientific problem of how to modulate the excitation and propagation of electromagnetic waves in media by using plasmon microstructures, this paper studies the mechanism and structure design scheme of high-efficiency broadband photon capture using artificial metal microstructures, and explores the optical absorption and local field enhancement synergy of plasmon excitations. The first part of this paper is the theoretical design and experimental fabrication of a two-dimensional disordered colloidal crystal-based metal micro-nano structure, so as to achieve wavelength-tunable ultra-wideband, incident angle and polarization-insensitive plasmon resonance perfect absorber. Aiming at the problems of quantum well photodetectors in infrared optical coupling efficiency, a kind of optical coupler for multilayer quantum wells operating in very long wave infrared (14-16 micron) band was designed by using the coupling effect of hybrid surface plasmon resonance mode and microcavity mode. The optical coupling efficiency was greatly improved. In the third part of this paper, we combine nanoimprinting technology with improved nano-lithography technology and metal nanoparticle deposition technology to fabricate a series of metal nanoparticle arrays with large area and high homogeneity, and explore their regulation on surface-enhanced Raman scattering (SERS) effect. Based on the self-organization technique of large-plane homogeneous disordered two-dimensional colloidal crystals, a broadband plasmon-photon perfect absorption structure is designed and fabricated. The structure is obtained by disorderly arrangement of two-dimensional colloidal crystals on a flat gold film and deposition of different thickness of gold film. The total absorption properties of the structure are derived from plasma exciton coupling. The excitation of the combined Fabry-Perot resonance mode and the magnetic plasmon cavity mode can produce a wider band of perfect absorption than the disordered plasmon-photon absorber in the ordered structure system because the Bloch eigenmode is suppressed by the disordered lattice. The hybrid arrangement of colloidal microspheres utilizes the influence of geometrical size on the regulation of optical absorption to achieve the perfect absorption of near-infrared ultra-wideband effectively. At the same time, due to the symmetry of a single resonant unit and the disordered arrangement of the system, the near-infrared full absorber exhibits the characteristics of polarization-independent and wide-angle response. The designed system is based on mature metal film deposition and colloidal crystal self-assembly method. It has the advantages of low preparation process requirements, cost control and high repeatability. By changing the size of microspheres and the thickness of metal film, the ultra-wideband total absorber can be operated in the full band from light to infrared. 2. Quantum well infrared detectors (QWIPs) have significant advantages over conventional HgCdTe infrared detectors in fabricating large-area, low-power, low-cost, high-uniformity and high-sensitivity focal plane array (FPA) imaging systems. However, for n-type QWIPs, due to the selection of inter-band transitions, Quantum well layers can not be coupled to vertically incident electromagnetic waves. In this paper, an efficient metal optical coupling structure for multilayer quantum well photodetectors in very long wave infrared band is proposed. The coupling structure supports two resonant modes, hybrid surface plasmon resonance and microcavity resonance, by adjusting the two modes. Coupling effectively enhances the photon density of states in the active region of quantum wells, especially the Ez component of the electric field, and improves the optical coupling efficiency of QWIPs. The coupling efficiency factor (_) of the Ez distribution in the layers reaches 6. In addition, the metal microstructures we designed exhibit the applicability of large incident angles (up to 40 degrees) and the dependence on the incident polarization. Based on the numerical simulation, we propose a combination of molecular beam epitaxy and standard light. A series of large-area, highly homogeneous metal nanoparticle arrays have been fabricated as SERS substrates based on nanoimprinting and improved nano-ball lithography. Firstly, we introduce the fabrication of SERS substrates with high-performance infrared photodetectors. A SERS substrate consisting of gold/PC nano-column arrays based on alumina template nanoimprinting and metal nano-particle deposition techniques was prepared. The optical properties of gold/PC nano-column arrays were adjusted by adjusting the structural parameters and the thickness of gold plating on AAO template. This kind of gold/PC nano-column array is actually situated on the elastic PC film, so the external force distortion and stretching will provide another degree of freedom for SERS. Secondly, we introduce an improved nano-ball lithography technique. A quasi-three-dimensional metal mesh SERS substrate with a large number of sub-nanometer ultra-small gaps has been fabricated. The substrate has a Raman enhancement factor of 1.5 *108 and can detect R6G molecules in aqueous solutions with concentrations as low as 1 *10-9M. The relative standard deviation (RSD) of the SERS strength distribution with spatial position is only 10.5%, showing excellent SERS performance. In addition, we have fabricated a large area of silver particle arrays on silicon wafers based on phase separation lithography. The arrays exhibit high homogeneity and Raman enhancement of 1.64 *108. In addition, compared with traditional methods, the method of preparing SERS substrate by phase separation lithography is simple, low-cost and has obvious yield. Industry application prospects.
【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB383.1;TG111
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