内嵌凹槽对金属亚波长狭缝透射特性的影响

研究了在特定入射波长852nm下内嵌凹槽结构对金属亚波长透射特性的影响.结果表明,内嵌凹槽结构的金属狭缝呈现透射增强或减弱的现象主要取决于凹槽的几何参数和位置.在凹槽和狭缝处会激发出SPPs,激发出的SPPs与入射波相互作用.同时,狭缝和凹槽都会形成谐振腔.凹槽的几何参数和位置的变化会影响SPPs的相位和SPPs与入射光的耦合,且随着谐振腔中共振模式的改变,透射谱呈现出不同程度的增强或减弱现象.研究结果有助于提高亚波长金属结构的透射率,同时有助于进一步探索SPPs的作用机制和狭缝结构的透射增强机理.     

凹槽导体上的表面等离激元SPPs传输特性研究

紫外段的光波从空气里入射到导体上,除部分光被反射,导体同时也对光波进行了宽带吸收而产生溅射的表面等离激元SPPs, SPPs在导体表面产生了亚波长约束可形成强电场,其有超衍射、敏感传播面上的细微变化、磁响应增强等特色性能.文章采用Maxwell电磁场方程组,对紫外段光波在导体传播面上产生的等离激元SPPs机制、刻有一维周期凹槽导体上的微波段SPPs传输色散特性,进行了推导、计算,仿真出三维凹槽同轴波导的场分布,得出了在符合波矢匹配条件下,可把微波段的导行电磁波,通过波导的亚波长周期凹槽转化成SPPs传输.     

基于圆角矩形结构的表面等离子体激元滤波器与光开关

本文提出并研究基于圆角矩形结构的表面等离子体激元带通滤波器，运用时域有限差分方法(Finite-Difference Time-Domain ,FDTD)对滤波器的透过率特性进行模拟仿真.由于采用圆角矩形结构，滤波器的透过率在带宽不变的情况下被优化.通过改变圆角矩形谐振腔的圆角半径以及腔长，可以实现所需要的透过率光谱. 本文在圆角矩形结构基础上提出12解复用器，通过将输出端2与谐振腔耦合处的波导增长120nm，实现了抑制共振模作用. 通过在滤波器的圆角矩形谐振腔中注入具有双折射效应的液晶Merck BL009，提出具有波长选择作用的光开关. 以上实验结果表明，基于圆角矩形结构的等离子体激元滤波器在纳米光学器件中具有很好的应用前景.     

基于矩形谐振腔MIM波导结构的表面等离子体带阻滤波器

采用二维时域有限差分法(FDTD)设计并验证了一种新型的基于金属-介质-金属(metal-insulator-metal,MIM)多矩形谐振腔结构的表面等离子体带阻滤波器.该结构由一波导通道和一列平行排列于波导上方的矩形谐振腔组成.当矩形腔的长度对某一波长满足法布里-珀罗(F-P)谐振条件时,该波长的表面等离子体(Surface Plasmon Polaritons,SPPs)将进入腔内并发生耦合共振而被限制在其内,起到滤波的效果.通过调整谐振腔的长度和数量,可以方便地滤掉一个或多个不同波长的光波.与其他结构SPPs滤波器相比,此结构更具有简洁、滤过的波长更窄、更小的能量损耗等优点,该种滤波器可以应用于高集成电路等光学设备.     

基于生物组织偏振特性的肝癌检测方法

肝细胞性肝癌属于原发性肝癌的一种,在我国发病率较高,且发病隐匿。癌变组织的组织结构和细胞形态会发生改变,这种亚波长微观结构的改变可以通过生物组织的偏振特性进行表达。根据光与生物组织相互作用原理,设计生物组织偏振成像系统,对30μm厚的未染色肝细胞性肝癌切片进行成像,借助与组织作用后背向散射光的偏振差异来表征生物组织的结构差异。实验结果表明,在各起偏角度的线偏振度图像中,肝癌组织与肝硬化组织的对比度较普通强度图像平均提升91%,最高提升155%,在切片较厚、未染色条件下线偏振度成像方法具有区分癌变组织和非癌变组织的能力,为肝癌的病理检测提供了一种新的思路。     

磁性介质表面电磁波特征

根据电与磁的对称性,类比于表面等离子体(SPPs)的性质,本文研究了磁性材料与介质界面的表面电磁波特征.我们称这种表面电磁波为磁表面等离子体(MSPP).本文推导了磁表面等离子体的波矢,并分析了MSPP的波长、传播距离以及穿透深度随磁性材料磁导率的变化,整理了单界面处MSPP在微波波段下的性质.     

表面等离子体狭缝波导上的石墨烯光电探测器

基于表面等离子体的硅基集成光电探测器因具有THz带宽潜力而受到广泛关注.本文基于简化的两步光刻工艺实现表面等离子体狭缝波导与石墨烯相结合的光电导探测器,直接采用对称的狭缝波导金属作为微波电极,理论计算3-dB带宽大于120 GHz,受限于测试设备,实际测试的带宽大于70 GHz,实验上实现了72 Gbit/s NRZ和64 Gbit/s PAM-4等高速信号的接收,误码率均低于15%的软判决前向纠错码门限.由于表面等离子体增强了光和石墨烯的相互作用,在吸收区长度不大于7μm和偏置电压0.4 V的条件下,探测器的响应度大于0.13 A/W.该探测器解决了目前表面等离子体探测器普遍存在工艺复杂、高速性能受限于吸收材料载流子动态特性的问题,具备超小尺寸、高速大带宽、工艺简单和与CMOS工艺兼容的特点,有望在高速光互连、太赫兹发射以及太赫兹通信中得到应用.     

硅基PMMA/SiO2-ZrO2有机-无机复合光波导的制备研究

构建了一种硅基PMMA/SiO2-ZrO2有机-无机复合光波导结构,采用溶胶-凝胶法在硅基底上制备厚度约17μm的PMMA薄膜作为包层材料,在硅基PMMA上制备了具有紫外感光性的SiO2-ZrO2基有机-无机复合芯层薄膜.测得PMMA和SiO2-ZrO2基复合薄膜在光纤常用通讯窗口0.85,1.31,1.55μm波长附近的折射率差比δ分别为4.81%,4.55%,4.50%.利用芯层材料自身的感光性,结合紫外辐照技术,制备了硅基PMMA/SiO2-ZrO2基有机-无机复合光波导阵列图形,其最小宽度约25μm,厚度约5μm,图形规整、边缘清晰.通光实验表明该波导能够将波长1.53~1.55μm的光限制在波导内,实现光的传输和分束.     

非周期高透射亚波长会聚光栅的研究

亚波长光栅作为一种新颖的光学器件可以实现光束的偏转、功分、会聚、偏振分束等功能.针对空间光的耦合以及微型激光器输出光的束型需求,本文提出了一种具有透射光束会聚效果的一维亚波长光栅,通过对亚波长光栅的结构设计,控制亚波长光栅的波前相位使得亚波长光栅具有高的透射率,以实现透射光束的会聚效果.利用有限元分析法(FEM)对设计的一维非周期亚波长会聚光栅数值进行仿真,结果表明:仿真焦距在10μm处的光束会聚的透射光栅,仿真得到的实际焦距fx为7.715μm,透射率为81.8%.因此,利用有限元法设计的非周期光栅对发散光束具有优异的会聚效果,有望在光通信器件的集成以及空间光耦合领域得到重要应用.     

浅谈倏逝波

倏逝波（Evanescent Wave）是一种非辐射近场波,包含很多近场精细结构信息,是近场光学研究的核心内容。倏逝波与表面等离子体激元（Surface Plasmon Polaritons,SPPs）的新颖结合,引起了研究者们的许多关注,在SPPs元器件和回路、纳米波导、SPPs光开关等方面具有很广阔的应用前景。文章介绍了倏逝波的存在条件和相关性质,并简述了与SPPs结合的相关应用。     

Surface plasmon subwavelength optics

Surface plasmons are waves that propagate along the surface of a conductor. By altering the structure of a metal's surface, the properties of surface plasmons--in particular their interaction with light--can be tailored, which offers the potential for developing new types of photonic device. This could lead to miniaturized photonic circuits with length scales that are much smaller than those currently achieved. Surface plasmons are being explored for their potential in subwavelength optics, data storage, light generation, microscopy and bio-photonics.     

Gate-tuning of graphene plasmons revealed by infrared nano-imaging

Surface plasmons are collective oscillations of electrons in metals or semiconductors that enable confinement and control of electromagnetic energy at subwavelength scales. Rapid progress in plasmonics has largely relied on advances in device nano-fabrication, whereas less attention has been paid to the tunable properties of plasmonic media. One such medium--graphene--is amenable to convenient tuning of its electronic and optical properties by varying the applied voltage. Here, using infrared nano-imaging, we show that common graphene/SiO(2)/Si back-gated structures support propagating surface plasmons. The wavelength of graphene plasmons is of the order of 200 nanometres at technologically relevant infrared frequencies, and they can propagate several times this distance. We have succeeded in altering both the amplitude and the wavelength of these plasmons by varying the gate voltage. Using plasmon interferometry, we investigated losses in graphene by exploring real-space profiles of plasmon standing waves formed between the tip of our nano-probe and the edges of the samples. Plasmon dissipation quantified through this analysis is linked to the exotic electrodynamics of graphene. Standard plasmonic figures of merit of our tunable graphene devices surpass those of common metal-based structures.     

Low-energy acoustic plasmons at metal surfaces

Nearly two-dimensional (2D) metallic systems formed in charge inversion layers and artificial layered materials permit the existence of low-energy collective excitations, called 2D plasmons, which are not found in a three-dimensional (3D) metal. These excitations have caused considerable interest because their low energy allows them to participate in many dynamical processes involving electrons and phonons, and because they might mediate the formation of Cooper pairs in high-transition-temperature superconductors. Metals often support electronic states that are confined to the surface, forming a nearly 2D electron-density layer. However, it was argued that these systems could not support low-energy collective excitations because they would be screened out by the underlying bulk electrons. Rather, metallic surfaces should support only conventional surface plasmons-higher-energy modes that depend only on the electron density. Surface plasmons have important applications in microscopy and sub-wavelength optics, but have no relevance to the low-energy dynamics. Here we show that, in contrast to expectations, a low-energy collective excitation mode can be found on bare metal surfaces. The mode has an acoustic (linear) dispersion, different to the dependence of a 2D plasmon, and was observed on Be(0001) using angle-resolved electron energy loss spectroscopy. First-principles calculations show that it is caused by the coexistence of a partially occupied quasi-2D surface-state band with the underlying 3D bulk electron continuum and also that the non-local character of the dielectric function prevents it from being screened out by the 3D states. The acoustic plasmon reported here has a very general character and should be present on many metal surfaces. Furthermore, its acoustic dispersion allows the confinement of light on small surface areas and in a broad frequency range, which is relevant for nano-optics and photonics applications.     

基于表面等离激元的量子相干效应的理论研究

起源于金属中自由电子集体振荡的表面等离激元,具有超小的光学模式体积和亚波长局域的近场增益,为纳米尺度上研究光和物质相互作用带来新的机遇．共振的纳米金属结构的近场区域,具有各向异性的珀塞尔系数,并且可以为量子体系提供近场激发．我们理论上演示了基于表面等离激元结构的单分子共振荧光、原子布居数的本征量子拍频及其在表面等离激元结构中的纳米尺度上的实现、表面等离激元诱导的各向异性珀塞尔系数导致的亚波长尺度自发辐射谱线的变化．这些结果在超紧凑的有源量子器件中有潜在应用．     

Thermal detection of surface plasmons on gold nanohole arrays

We used a thin-film thermocouple to detect the thermal effect of surface plasmons excited in Au nanohole array structures.We found that the thermal electromotive force of Au film with periodic nanohole structures is three times greater than that of a bare Au film for 785-nm laser excitation at a given power.This effect is caused by the resonant excitation of localized surface plas- mons in the nanoholes.In addition,we found that the thermal electromotive force(EMF)of the Au film with dumbbell-like na- nohole arrays depends strongly on the incident polarization.The thermal EMF is the greatest when the excitation light is polarized perpendicular to the long axis of the dumbbell.     

局域表面等离子体研究进展

阐述了局域表面等离子体特性,金属纳米粒子的常用制备方法,以及不同形状、尺寸等因素对局域表面等离子体光谱和灵敏度的影响,分析了表面增强拉曼散射的增强因子与金属纳米粒子的等离子共振波长和拉曼激发波长之间的关系,介绍了局域表面等离子体在生物传感方面的应用.     

Generation of single optical plasmons in metallic nanowires coupled to quantum dots

Control over the interaction between single photons and individual optical emitters is an outstanding problem in quantum science and engineering. It is of interest for ultimate control over light quanta, as well as for potential applications such as efficient photon collection, single-photon switching and transistors, and long-range optical coupling of quantum bits. Recently, substantial advances have been made towards these goals, based on modifying photon fields around an emitter using high-finesse optical cavities. Here we demonstrate a cavity-free, broadband approach for engineering photon-emitter interactions via subwavelength confinement of optical fields near metallic nanostructures. When a single CdSe quantum dot is optically excited in close proximity to a silver nanowire, emission from the quantum dot couples directly to guided surface plasmons in the nanowire, causing the wire's ends to light up. Non-classical photon correlations between the emission from the quantum dot and the ends of the nanowire demonstrate that the latter stems from the generation of single, quantized plasmons. Results from a large number of devices show that efficient coupling is accompanied by more than 2.5-fold enhancement of the quantum dot spontaneous emission, in good agreement with theoretical predictions.     

乳酸菌内化小鼠小肠派伊尔结特性及其影响因素

为了探索乳酸菌表面物理化学性质和红细胞凝集性与其内化派伊尔结(PP)之间的关系,分别用细菌黏附正十六烷法(BATH)、ε电位仪、接触角和液体表面张力测定疏水性、细胞表面电荷和表面自由能;并用兔红细胞凝集活性评价乳酸菌表面凝集素表达性质;3H标记的乳酸菌,分析其在PP内化的能力,并在体内分析了3H标记的三株乳杆菌体内内化于PP的性质。体外试验证明,22株乳酸菌体外内化PP的性质具有显著的菌株特异性;细菌的疏水性和内化PP的能力没有相关性;而细菌的表面自由能和内化PP的能力呈负相关趋势。选用的4株乳酸菌在体内内化PP的能力也和体外的结果一致。乳酸菌内化PP的能力具有菌种依赖性。细菌表面电荷、疏水性和红细胞凝集能力与内化能力之间没有相关关系,但细菌的表面自由能与内化能力呈负相关趋势。     

Thermal radiation scanning tunnelling microscopy

In standard near-field scanning optical microscopy (NSOM), a subwavelength probe acts as an optical 'stethoscope' to map the near field produced at the sample surface by external illumination. This technique has been applied using visible, infrared, terahertz and gigahertz radiation to illuminate the sample, providing a resolution well beyond the diffraction limit. NSOM is well suited to study surface waves such as surface plasmons or surface-phonon polaritons. Using an aperture NSOM with visible laser illumination, a near-field interference pattern around a corral structure has been observed, whose features were similar to the scanning tunnelling microscope image of the electronic waves in a quantum corral. Here we describe an infrared NSOM that operates without any external illumination: it is a near-field analogue of a night-vision camera, making use of the thermal infrared evanescent fields emitted by the surface, and behaves as an optical scanning tunnelling microscope. We therefore term this instrument a 'thermal radiation scanning tunnelling microscope' (TRSTM). We show the first TRSTM images of thermally excited surface plasmons, and demonstrate spatial coherence effects in near-field thermal emission.     

体极化介质IP面电荷的计算及分布规律

本文以等效电阻率法为理论基础,导出了几种常见情况下,体极化介质表面上一次电流场和二次极化电流场以及总电流场的面电荷密度的表达公式,并分别对点电流源场中多层介质分界面上的面电荷密度及在均匀电流场中球状和水平圆柱状极化体表面上的面电荷密度进行了具体计算,得到了某些表征电荷分布规律的理论曲线。利用本文中给出的研究结果,可以简便地对一次电流场和二次极化电流场的异常电位及异常电流强度的分布特征,进行定性分析和定量研究。