A new positioning approach of fiber probe for near-field scanning optical microscope

A fiber probe-based positioning scan approach was established, whose precision can reach as high as 0.8 μm. And a set of modified microscope system was designed utilizing this approach, in which the scanning probe microscope (SPM) combined with an optical microscope was manipulated. The optical microscope and scanning probe can conveniently be switched through a switch panel. The observation period of samples can significantly be shortened. And more reliable images can be provided using this approach. Our design can effectively solve the inherent disadvantages of SPM technology, which makes SPM scan and image more reliably, conveniently, safely and rapidly.     

Recent developments in nanofabrication using scanning near-field optical microscope lithography

In addition to its well-known capabilities in imaging and spectroscopy, scanning near-field optical microscopy (SNOM) has recently shown its great potentials for fabricating various structures at the nanoscale. A variety of SNOM-based fabrication techniques have been developed for different applications. In this paper, the SNOM-based techniques involving three major functions: material modification, addition, and removal, are examined with emphasis on their abilities and reliability to make structures with resolutions at the nanometer level. The principles and procedures underlying each technique are presented, and the differences and uniqueness among them are subsequently discussed. Finally, concluding remarks are provided to summarize the major techniques studied and to recommend the scopes for technology improvement and future research.     

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.     

Image dipole approach and polarization effects in scanning near-field optical microscopy

A coupled-dipole approach is proposed in order to study the coupling between the probe tip and the rough sample in SNOM. In the present model both the optical probe tip and the sample protrusions are represented by polarizable dipole spheres. The induced polarization effects on the sample surface can be replaced by the image dipoles in the circumstance of quasi-static electromagnetic field approximation. Applying the radiation theory of the dipole, we have established a set of self-consistent equations to describe the field distribution at the sites of the probe tip and the sample protrusions. The results are completely the same as those obtained by means of the dyadic electromagnetic propagator formalism and also the derivation procedure is relatively simple. This method permits us to analyze the physical mechanisms of the interaction between the probe tip and the rough surface in SNOM intuitively. Based on this approach, we further discuss the influence of polarization of the incident light on the imaging quality. The calculating result shows that the shape and the contrast of the images of the sample are both sensitive to the field polarization, and the z-polarized mode is proved to give better resolution in SNOM.     

High-sensitivity piezoelectric tube sensor for shear-force detection in scanning near-field optical microscopy

An easy-to-implement non-optical shear-force detection setup for tip–sample distance regulation in scanning near-field optical microscopy is demonstrated. The detection method is based on attaching the near-field probe to a piezoelectric tube resulting in excellent mechanical contact between tip and detector. The main advantages of the method are good signal-to-background contrast and thus potential for high sensitivity. The method is demonstrated by obtaining approach curves of silicon surfaces. The suitability for optical experiments is further shown by measuring the near-field intensity distribution of the emission of a semiconductor laser.     

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.     

The coaxial tip as a nano-antenna for scanning near-field microwave transmission microscopy

A novel scanning-probe setup is reported that maps the complex transmission of microwaves. Response to topographic features as small as 15 nm was observed. The sharpened coaxial probe tip serves as a microwave antenna and, at the same time, as a tunnel tip to warrant precise distance control by STM (scanning tunneling microscope) feedback. The instrument can be applied to map the microwave conductivity of, e.g. thin films or low-dimensional semiconductors. Consequences for the development of an infrared microscope are outlined.     

Review of near-field optical microscopy

This review has introduced a new near-field optical microscope (NOM)—atomic force microscope combined with photon scanning tunneling microscope (AF / PSTM). During scanning, AF/PSTM could get two optical images of refractive index image and transmissivity image, and two AFM images of topography image and phase image. A reflected near-field optical microscope (AF/RSNOM) has also been developed on AF/PSTM platform. The NOM has been reviewed in this paper and the comparison between AF/PSTM & RSNOM and the commercial A-SNOM & RNOM has also been discussed. The functions of AF/PSTM & RSNOM are much better than A-SNOM & RNOM.     

Imaging of human meiotic chromosomes by scanning near-field optical microscopy (SNOM)

Centromeres and telomeres are key structures of mitotic and meiotic chromosomes. Especially telomeres develop particular structural properties at meiosis. Here, we investigated the feasibility of scanning near-field optical microscopy (SNOM) for light-microscopic imaging of meiotic telomeres in the sub-hundred nanometer resolution regime. SNOM was applied to visualise the synaptonemal complex (SC) and telomere proteins (TRF1, TRF2) after differential immuno-fluorescent labelling. We tested and compared two different preparation protocols for their applicability in a SNOM setting using micro-fabricated silicon nitride aperture tips. Protocol I consisted of differential labelling of meiotic chromosome cores (SC) by SCP3 immuno-fluorescence and telomeres by TRF1 or TRF2 immuno-fluorescence, while protocol II combined absorption labelling with alkaline phosphatase substrates of cores with fluorescent labelling of telomeres. The results obtained indicate that protocol I reveals a better visualisation of structural (topographic) details than protocol II. By means of SNOM, meiotic chromosome cores could be visualised at a resolution overtopping that of far-field light microscopy.     

Dual mode near-field scanning optical microscopy for near-field imaging of surface plasmon polariton

In this paper, we theoretically and experimentally demonstrate that metal coated apertured probes are efficient near-field probes on surfaces with high reflectivity for the scattering as well as for the collection mode near-field scanning optical microscopy (NSOM). We show that a blunt apertured metal coated tip is very effective in suppressing image dipoles which affect strongly the signals scattered from frequently used sharp metal tips or gold nanoparticle attached probes. By using a simultaneous collection and scattering mode (dual mode) NSOM we measure the near-field images of surface plasmon polariton (SPP) launched from a slit. The collection mode measures propagating SPP along lateral distance in a long scan range with high signal-to-noise ratio, and the scattering mode measures the polarization resolved near-field of SPP. Comparisons of the measured data obtained in the dual mode enable to easily characterize SPP and to separate the measured near-field into the propagating SPP and the directly transmitted light.     

Direct observation of variations of optical properties in single quantum dots by using time-resolved near-field scanning optical microscope

We study the variations of optical properties of self-assembled In_0.5Ga_0.5As single quantum dots (QDs) in the spatial and time domains by combining a near-field scanning optical microscope with an ultrafast pulsed laser. Through the examinations of several tens of QDs, we find that the variations of photoluminescence (PL) intensity strongly depend on the condition of the initial carrier creation. The differences in quantum efficiency and those in the carrier flow rate into QDs cause the large distribution of PL intensity when the carriers are excited in the barrier layers. From the results of time-resolved PL decay measurements, we find that there are two types of QDs exhibiting quite different PL decay profiles.     

带金属尖四棱锥小孔光探针光斑近场分布数值模拟

采用时域有限差分法(FDTD)研究了带金属尖四棱锥小孔光探针光斑近场分布特性,分析了金属尖的长度、尖端半径及距离小孔位置等因素对近场电场分布的影响.讨论了该类光探针的电磁波通过等离子体激元方式从小孔传输到金属尖的机理.Taminiau等人用不同方法获得的计算结果在本文的计算结果中得到了印证.在此基础上,本文重点分析、讨论了Pohl等人在1984—1986年获得20—25nm高分辨率图像的原由,讨论了该实验系统的成像机理和类型的归属.计算结果表明:Pohl等人的实验系统成像机理已离开小孔径扫描近场光学显微镜类型,报告认为应归属金属尖散射扫描近场光学显微镜一类.本结果对设计性能优良的光探针具有参考意义.     

Nano-optical image and probe in a scanning near-field optical microscope

We study a nanometer-sized optical probe and image in a scanning near-field optical microscope (SNOM). We demonstrated the potential to observe 5-nm wide optical patterns using the SNOM. The probe profile was measured by using a knife-edge method and a modulated transfer function evaluation method. An aluminum covered and pipet-pulled fiber probe used here has two optical probes, one which has a large diameter of 350 nm and one which has a small diameter of around 10 nm.     

Method of resonance near-field optical microscopy

We have solved the problem in which a thin metal wafer (probe) with a nanohole interacts with the flat surface of a metastructured film consisting of metal nanoparticles in an external optical radiation field. Nanoparticles are considered as two-level atomic systems. This interaction of the wafer-probe and the flat surface in the external optical radiation field gives rise to optical near-field resonance, the frequency of which differs significantly from the natural frequencies of two-level atoms in the medium and the probe. The fields inside and outside the probe and metastructured film are calculated in the near-field and far-field zones. The maximum resolution, which is achievable in the suggested scheme of near-field optical microscopy, can reach about 10 nm. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 499–506, July–August, 2007.     

A resonance tracking method for stable operation of a near-field scanning optical microscope in liquid environment

We report on the novel design of the near-field scanning optical microscope (NSOM) which operates in liquid environment. A resonance tracking digital scanning method is applied to compensate the resonance shift due to the evaporation of the liquid in the atmospheric pressure. By this method, stable operation of NSOM system is demonstrated by showing topographic images of the metallic grating embedded in liquid environment.     

飞秒时间分辨近场光学系统实现及其应用

结合飞秒光脉冲和近场光学显微镜，成功实现了飞秒时间分辨近场光学系统.系统通过高频声光调制和差频锁相探测，极大提高了信噪比并消除了抽运、探测光本底信号，从而在收集模式下测得了飞秒时间分辨的透射光微弱信号变化.同时获得了80nm的空间分辨和小于200fs的时间分辨测量.利用该实验系统，研究了金纳米结构的热电子弛豫动力学过程，观察到不同位置间热电子弛豫动力学的差异. 关键词： 飞秒近场 扫描近场光学显微镜 飞秒光脉冲 金纳米颗粒     

超小自聚焦光纤探头的研究进展

梯度折射率（Gradient-index,GRIN）光纤探头是一种全光纤型超小光学镜头,在心血管等狭小空间组织内窥影像检测中具有广阔的应用前景。但其发展一直缺少系统的理论体系。本文讨论探头设计、制作和性能测试等方面的关键问题。基于GRIN光纤探头聚焦性能的特征参数,对解析设计方法与数值仿真设计方法进行比较分析。针对超小GRIN光纤探头的制作难题,研究一种光纤熔接和切割的高精度一体化集成装置,描述GRIN光纤探头的制作方法。此外,分析了超小GRIN光纤探头聚焦性能检测的方法及装置。本文为超小GRIN光纤探头的设计、制作及性能测试提供了一个方法体系。     

利用扫描近场红外显微镜对化学样品组分进行成像研究

介绍了用北京自由电子激光为光源的扫描近场红外显微镜对化学样品组分进行的成像研究，通过所得到的近场微区图像，可以对样品在微区范围内的成分组成，混合的均匀程度等作出比较清晰的判断. 关键词： 自由电子激光 近场光学 扫描近场红外显微镜