一种探针-样品距离的切变力控制新方法

报道了近场扫描光学显微镜(Near-filed Scanning Optics Microscope-NSOM)中一种基于切变力的探针-样品间距控制新方法.条形压电蜂鸣器片的上表面电极被沿着中心线分成两半,一半用于驱动,其上施加振荡源谐振频率进行激励,另一半上粘附光纤探针,并利用压电效应作为光纤探针的振幅传感器.当受振动激励的光纤探针由远处逐渐接近样品表面时,由于样品与探针之间的切变力阻尼作用使得探针的振幅减小,通过检测探针振幅的变化可以控制探针与样品的间距.我们建立了一套探针-样品间距探测控制系统并利用该系统获得了CD盘片表面8μm×8μm范围内的切变力形貌图.     

一种探针-样品距离的切变力控制新方法

报道了近场扫描光学显微镜(Near-filed Scanning Optics Microscope NSOM)中一种基于切变力的探针 样品间距控制新方法.条形压电蜂鸣器片的上表面电极被沿着中心线分成两半,一半用于驱动,其上施加振荡源谐振频率进行激励,另一半上粘附光纤探针,并利用压电效应作为光纤探针的振幅传感器.当受振动激励的光纤探针由远处逐渐接近样品表面时,由于样品与探针之间的切变力阻尼作用使得探针的振幅减小,通过检测探针振幅的变化可以控制探针与样品的间距.我们建立了一套探针 样品间距探测控制系统并利用该系统获得了CD盘片表面8μm×8μm范围内的切变力形貌图.     

近场扫描光电显微镜中一种新的切向力检测系统

在近场扫描光学显微镜（ＮＳＯＭ）＾［１］中,近场距离控制一般要用切向力控制法。检测切向力有两种方法：光学检测法和非光学检测法。目前普遍采用非光学检测法,基本上是采用压电陶瓷管控制探针和样品的距离。本文提出一种新的切向力检测系统,利用双压电片实现近场距离控制。实验结果表明,检测灵敏度大大提高,扫描力显微（ＳＦＭ）像的分辨率可达纳米量级。     

近场扫描光学显微镜中一种新的切向力检测系统

在近场扫描光学显微镜（ＮＳＯＭ）［１］中,近场距离控制一般采用切向力控制法。检测切向力有两种方法：光学检测法和非光学检测法。目前普遍采用非光学检测法,基本上是采用压电陶瓷管控制探针和样品的距离。本文提出一种新的切向力检测系统,利用双压电片实现近场距离控制。实验结果表明,检测灵敏度大大提高,扫描力显微（ＳＦＭ）像的分辨率可达纳米量级。     

内窥式二维光纤扫描探头及其驱动方法

基于压电换能器技术设计了一种应用于光学相干层析成像的新型内窥式二维光纤扫描探头,即利用两片压电陶瓷片和一片薄导电基片驱动光纤探头.该探头利用光纤悬臂的共振特性,通过对压电陶瓷施加等于光纤共振频率的混频信号,能同时激发光纤悬臂两正交方向上的振动,可以实现光纤悬臂的二维扫描.建立了理论模型并进行了有限元仿真分析,最后搭建了实验系统,验证并获得了扫描图样.实验结果实现了光纤悬臂的二维扫描,扫描范围达到(500×500)μm,调节驱动信号振幅幅值可以调节扫描范围.实验结果与理论分析和仿真相吻合,验证了方案的可行性.     

基于半导体纳米线/锥形微光纤探针的被动式近场光学扫描成像

本文结合近场扫描结构和纳米线-微光纤耦合技术,提出了一种基于硫化镉纳米线/锥形微光纤探针结构的被动近场光学扫描成像系统.该系统采用被动式纳米探针,保留了纳米探针对样品表面反射光的强约束优势.其理论收集效率为4.65‰,相比于传统的金属镀膜近场探针收集效率提高了一个数量级,可有效地提高扫描探针对样品形貌信息的检测能力;而后通过硫化镉纳米线与微光纤之间高效的倏逝场耦合,将检测的光强信号传输到远场进行光电探测,最终实现对目标样品形貌的分析成像,其样品宽度测量误差在7.28%以内.该系统不需要外部激发光路,利用显微镜自身光源进行远场照明,被动扫描探针仅作为样品表面反射光的被动收集系统.本文基于半导体纳米线/锥形微光纤探针的被动式近场光学扫描成像方案,可有效地降低探针的制备难度和目标光场的检测难度,简化扫描成像的结构,为近场光学扫描显微系统之后的发展提供新的思路.     

基于半导体纳米线/锥形微光纤探针的被动式近场光学扫描成像

本文结合近场扫描结构和纳米线-微光纤耦合技术,提出了一种基于硫化镉纳米线/锥形微光纤探针结构的被动近场光学扫描成像系统.该系统采用被动式纳米探针,保留了纳米探针对样品表面反射光的强约束优势.其理论收集效率为4.65‰,相比于传统的金属镀膜近场探针收集效率提高了一个数量级,可有效地提高扫描探针对样品形貌信息的检测能力;而后通过硫化镉纳米线与微光纤之间高效的倏逝场耦合,将检测的光强信号传输到远场进行光电探测,最终实现对目标样品形貌的分析成像,其样品宽度测量误差在7.28%以内.该系统不需要外部激发光路,利用显微镜自身光源进行远场照明,被动扫描探针仅作为样品表面反射光的被动收集系统.本文基于半导体纳米线/锥形微光纤探针的被动式近场光学扫描成像方案,可有效地降低探针的制备难度和目标光场的检测难度,简化扫描成像的结构,为近场光学扫描显微系统之后的发展提供新的思路.     

内窥式二维光纤扫描探头及其驱动方法

基于压电换能器技术设计了一种应用于光学相干层析成像的新型内窥式二维光纤扫描探头,即利用两片压电陶瓷片和一片薄导电基片驱动光纤探头.该探头利用光纤悬臂的共振特性,通过对压电陶瓷施加等于光纤共振频率的混频信号,能同时激发光纤悬臂两正交方向上的振动,可以实现光纤悬臂的二维扫描.建立了理论模型并进行了有限元仿真分析,最后搭建了...     

剪切力模式近场扫描光学显微镜的恒幅反馈控制方法研究

剪切力模式近场扫描光学显微镜(Near-field Scanning Optical Microscopy,NSOM) 的音叉探针间距控制系统中,用相位反馈控制和检测剪切力,同时采用比例＋积分（PI）技术实现对音叉探针振幅的反馈控制,使探针振幅在扫描过程中保持为恒定值.用相位信号作为探针与样品间距控制信号,分别在无振幅反馈和有振幅反馈两种情况下,以不同速率扫描得到标准CD_RW光盘光栅的两组图像,并进行了比较分析.实验表明,恒振幅反馈电路的引入有助于提高探针系统的响应速度和灵敏度,改善所得图像的质量及分辨率.     

基于光导微探针的近场/远场可扫描太赫兹光谱技术

太赫兹技术已经成为涉及公共安全、军事国防和国民经济等国家核心利益的前沿研究领域.以往太赫兹测量技术中通常以远场测量为主,如常用的太赫兹时域光谱仪.近年来太赫兹近场技术得到了迅猛的发展,特别是基于光导天线的探针技术的发展,为可扫描的太赫兹近场测量提供了可能.本文详细报道了我们近期在可扫描太赫兹近场光谱仪研究中的进展.采用光纤耦合的光导微探针实现了方便灵活的太赫兹近场/远场三维扫描,并同时获得振幅和相位信息.该系统将有可能广泛应用于人工微结构、石墨烯、表面等离子激元、波导传输、近场成像、生物样品检测、芯片检测等研究领域.     

Role of the probe quadrupole moment in apertureless near-field optical microscopy

A theory of an apertureless scanning near-field optical microscope is developed that takes into account the quadrupole moment of the probe in forming the near field and the scattered wave in the far-field zone. It is shown that the quadrupole moment can lead to a change in the conditions for the resonant coupling of the probe tip with the sample surface, as well as to the appearance of additional resonances in the frequency dependence of the response of a near-field microscope. The theory developed is found to be in good agreement with known experimental data in the region of resonant tip—sample coupling.     

Nanometer-scale probing of optical and thermal near-fields with an apertureless NSOM

We have used a home-made apertureless near-field scanning optical microscope (ANSOM) for mapping nanometric steps between SiC and gold regions under visible (λ=655 nm) and infrared (λ=10.6 μm) illumination. The images, obtained with a signal demodulation at the tip oscillation frequency and at higher harmonics, clearly show optical contrasts with a subwavelength resolution of about 30 nm. Other images recorded in the visible on a YBa₂Cu₃O₇ crystal indicate that the tip used in our experiments is able to reveal polarization effects. We also present a near-field thermal optical microscope (NTOM) which operates without any external illumination. In this new kind of microscope, the laser source which is usually used to excite the evanescent waves, is replaced by a simple heating of the sample. The electromagnetic radiation locally scattered by the tip comes from the thermal radiation. Our results with this new technique prove a 200 nm lateral resolution.     

光纤探针型近场光镊光阱力特性研究

基于动量守恒原理,结合麦克斯韦应力张量和三维时域有限差分方法,建立了近场空间内激光光镊对纳米微粒的光阱力计算模型.分析了光纤探针型近场光镊的近场分布以及操作纳米微粒时各轴向光阱力的分布情况,并探讨了光纤探针尖端的捕获尺寸、捕获位置和操作稳定性.结果表明:微粒应处于光纤探针针尖的近场空间内才可实现稳定可靠的纳米操作,不同尺寸的微粒具有不同的捕获效果,且随初始位置的不同微粒的捕获位置亦不同.计算结果为激光近场光镊纳米操作装置的设计和制造提供了理论基础.     

金属覆层光纤探针近场特性研究

采用有限积分法对用于近场光学显微镜的旋转对称光纤探针进行了数值模拟计算,研究了光纤探针开口附近亚波长范围的电磁场及其能量密度的分布.计算结果表明,在探针外,光场为沿探针轴线方向的近逝波,其空间光场的分布与激励光场及其极化方向有关,在激励光场的极化方向出现了由感应电荷引起的边缘增强效应.同时研究了近场光纤探针的空间分辨率和样品处的电磁场能量,结果表明光纤探针孔的尺寸及其与样品的作用距离是影响探针的分辨率和样品内电磁场能量的重要因素.     

Near-field study of optical modes in randomly textured ZnO thin films

We report on near-field scanning optical microscopy measurements on randomly textured ZnO thin films. These films are commonly used as transparent conducting oxide in thin-film solar cells. Textured interfaces are used to increase the scattering of light, which leads to a better light trapping in the solar cell. Here, both the topography and the local transmission are measured with a tapered fiber tip with very high spatial resolution. By varying the distance of the tip and the wavelength of the incident light, the optical profile is visualized and reveals a strong confinement of light on a subwavelength scale which corresponds to ridges in the surface structure. The confinement of light results from guided optical modes in the ZnO which are accompanied by a modulated evanescent field in air. No corresponding structure to this modulation is found in the topography. These results give new insight for further improvement of light trapping in solar cells.     

单壁碳纳米管束针尖增强近场拉曼光谱探测实验研究

针尖增强近场拉曼光谱术是最近发展起来的光谱技术。金属探针在获得样品纳米局域表面形貌的同时,受激光激发,在针尖附近产生增强电磁场,得到与形貌位置精确对应的针尖增强局域拉曼光谱,形貌和光谱的结合实现了纳米局域的光谱指认。文章建立了一套针尖增强近场拉曼光谱测量装置,并用此装置对电弧法合成的单壁碳纳米管进行了近场拉曼光谱探测。测量了直径为100 nm单壁碳纳米管束的针尖增强拉曼光谱,进一步得到至多3根单壁碳纳米管的近场拉曼光谱,实现了超衍射分辨光谱探测。通过与远场拉曼光谱比较发现,针尖增强近场拉曼光谱的增强因子大于230倍。实验证明,同时具有超衍射空间分辨和拉曼光谱信号增强能力的针尖增强近场拉曼光谱术将是纳米材料和纳米结构表征的一种重要方法。     

Influence of the sample-probe coupling on the resolution of transmitted near-field optical image

Numerical simulation of photon scanning tunneling microscopy is presented to study the near-field distribution in the vicinity a dielectric surface with one-dimensional sub-wavelength structures. Multiple scattering between the probe tip and the sample has been taken into account implicitly by matching electromagnetic boundary conditions at interfaces. The near-field intensity in transmission mode through two ridges on surface has been modeled in order to analyze the resolution of the system. The effects on the signal by the sample-tip coupling, the polarization of the incident light, and the angle of incidence are investigated. We find that the capability to recognize the feature will be improved when the tip–object interaction is strong.     

Near-field imaging of pyramid-like nanoparticles at a surface

An exact analytical solution of the self-consistent equation for the local field is used to calculate the near-field optical images of pyramid-like nano-objects placed at a surface of a solid. The diagram method developed previously for near-field image formation is generalized in order to describe layered objects, which are treated as many-body systems. The near-field optical images of triangular and square pyramids are calculated for the illumination configuration as well as those of triangular and square prisms. It is found that the near-field images of nanoparticles having the dielectric constant close to that of the substrate change rapidly and in a complicated manner with the probe–sample distance.     

Plasmon resonance microsensor for droplet analysis

Microscale fiber tip sensors based on the plasmon resonance are reported. The fabrication process derived from our previous approach for manufacturing near-field scanning optical microscopy probes has been optimized for sensing applications. A typical tip sensor is a tapered fiber 400 microm in length, coated with a nanoporous thin silver film. The miniaturized geometry of the sensor allows detection in a single droplet of liquid solution (approximately 20 microl). The tip sensor is sensitive for refractive indices between 1.33 and 1.40 with a sensitivity of at least 3 x 10(-4) refractive index unit (RIU)/nm. The Raman scattering enhancement through these microsensors demonstrates the important role played by the localized plasmon resonance. The sensors' linear response covers a large region, interesting for biosensing in aqueous environments such as biomedical applications.     

近场头相关传递函数的数值计算与特性分析

建立了近场头相关传递函数(HRTF)的边界元算法,针对刚性圆球人头简化模型,利用解析计算结果对其进行了验证,然后依据GB/T2428-1998建立了一个椭球人头模型,利用边界元算法计算了中低频多个空间方位的近场HRTF,并对其随方位和距离的变化特性进行了分析。