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.     

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.     

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.     

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.     

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.     

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.     

掺杂CdS超微粒的ZrO2薄膜的光学性质

研究了用溶胶凝胶方法制备的CdS超微粒 ZrO2 薄膜的发光特性 ,测量了不同退火温度处理的样品的荧光光谱、荧光激发光谱和荧光衰减曲线的变化 ,通过荧光衰减曲线研究了 14 0 ps左右的CdS的带间跃迁发射和较慢的表面态发射。还测量了这种掺有CdS超微粒的ZrO2 薄膜的飞秒光克尔效应 ,得到三阶非线性光学极化率为4 4× 10 - 1 1 esu和大约 10 0fs的响应时间。结果表明 ,这类材料具有较大的光学非线性和快速的响应时间 ,在高速光开关等方面有潜在的应用前景     

纳米集成光路中的光源、光波导和光增强

使用近场光学显微术(scanning near-field optical microscopy, SNOM)研究了ZnO亚微米线端面出射性质,不同空间形貌Ⅱ-Ⅵ族半导体荧光器件光波导特性,二维光子晶体、准晶光子晶体对LED的出射增强作用以及表面等离激元(surface plasmon polariton, SPP)与半导体纳米荧光器件的相互作用,对纳米集成光路中的光源、光波导、光增强三个重要问题做了实验和理论上的分析.研究发现半导体微纳米线端面出射光束的质量与样品的直径有密切关系.通过合理地设计其直径和 关键词： 纳米集成光路 扫描近场光学显微术 光波导 光增强     

纳米集成光路中的光源、光波导和光增强

使用近场光学显微术(scanning near-field optical microscopy, SNOM)研究了ZnO亚微米线端面出射性质，不同空间形貌Ⅱ-Ⅵ族半导体荧光器件光波导特性，二维光子晶体、准晶光子晶体对LED的出射增强作用以及表面等离激元(surface plasmon polariton, SPP)与半导体纳米荧光器件的相互作用，对纳米集成光路中的光源、光波导、光增强三个重要问题做了实验和理论上的分析.研究发现半导体微纳米线端面出射光束的质量与样品的直径有密切关系.通过合理地设计其直径和     

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.     

Synthesis and Optical Characterization of CdS Nanowires by Chemical Process

Cadmium sulfide (CdS) nanostructured materials were synthesized by a wet chemical route without using any capping agent. X-ray diffraction pattern showed the typical interplanar spacings corresponding to the cubic phase of CdS. Transmission electron microscopy studies showed the nanowires formation with length in the range 0.1–1.5 μm and the diameter 25–30 nm. UV–visible optical spectroscopy study was carried out to determine the bandgap of the nanostructured CdS thin films and it showed blue shift with respect to the bulk value. Variation of band gap energies with annealing temperature was also studied in detail. Room temperature photoluminescence of the nano-CdS films was measured and the spectrum showed a broad band centered at ~567 nm, which originated from trap states existing in the forbidden energy gap.     

Optical near-field mapping of bright and dark quantum dot states

We theoretically investigate scanning near-field optical microscopy (SNOM) of semiconductor quantum dots. A general theoretical framework is developed that accounts for photo excitation and relaxation in complex dielectric environments. We find that in the near-field regime bright and dark excitonic states become mixed, opening new channels for the coupling to the electromagnetic field.     

CdS:Cu一维纳米结构及其光子学特性研究

利用化学气相沉积方法成功合成了CdS掺Cu的一维纳米结构,揭示了该掺杂纳米结构特殊的生长机制,发现了该结构新颖的光子学性质.实验表明,通过控制实验条件可以实现CdS中Cu离子掺杂,并可获得高质量的一维纳米结构.由于掺杂离子的影响,纳米结构在不同强度的光激发时表现出不同线形的发光光谱,掺杂浓度对发光峰的位置和相对强度有比较明显的影响,但对光谱线形影响不大.所得结果将有助于拓展CdS纳米结构在纳米光子学领域中的应用.     

远场光钳与近场光钳的发展

以经典光学为基础的光钳技术(又称"光镊")在生物、物理和化学等领域得到了广泛的发展和应用,但是该技术受到高倍显微物镜的尺寸和光学衍射极限等多种因素的制约,从而限制了其进一步发展。而远场光纤光钳和近场光钳技术,从不同方面克服了传统光钳的局限。回顾了传统光钳、远场光纤光钳和近场光钳的发展,着重讨论了各种方法的工作原理、实验方法和技术性能,对这几种光钳技术进行了深入地总结和细致地比较。     

Influence of the probe--sample interaction on scanning near-field optical microscopic images in the far field

We have studied the influence of probe--sample interaction in a scanning near-field optical microscopy (SNOM) in the far field by using samples with a step structure. For a sample with a step height of $\sim \lambda $/4, the SNOM image contrast between the two sides of the step changes periodically at different scan heights. For a step height of $\sim \lambda $/2, the image contrast remains approximately the same. The probe--sample interaction determines the SNOM image contrast here. The influence of different refractive indices of the sample has been also analysed by using a simple theoretical model.     

Mixed-solvothermal synthesis of CdS micro/nanostructures and their optical properties

Several novel cadmium sulfide (CdS) micro/nanostructures, including cauliflower-like microspheres, football-like microspheres, tower-like microrods, and dendrites were controllably prepared via an oxalic acid-assisted solvothermal route using ethylene glycol (EG) and H₂O as pure and mixed solvents with different S sources. The as-prepared products were characterized by X-ray powder diffraction (XRD), scanning electronic microscope (SEM) and UV-vis spectrophotometer (UV). It was found that CdS micro/nanostructures can be selectively obtained by varying the composition of solvent, concentration of oxalic acid, and sulfur sources. UV-vis absorption spectra reveal that their absorption properties are shape-dependent. The possible formation process of the CdS micro/nanostructures was briefly discussed. This route provides a facile way to tune the morphologies of CdS over a wide range.     

Self-Absorption Effect in the Spatial Resolved Spectra of CdS Nano-Ribbon Optical Waveguide Observed by Near-Field Spectroscopy

Scanning near-field optical microscopy (SNOM) and spectroscopy were used to study the light emission characteristics of CdS nano-ribbon optical waveguide. A continuous red-shift of photoluminescence (PL) spectra of such nano-ribbons with the increase of the light propagation distance was observed. Near-field optical images indicate that CdS nano-ribbon can work well as an optical waveguide. Quantitative calculation was made to demonstrate the PL attenuation with long propagation distance (typically several hundreds μm). The red shift is attributed to self-absorption, which means re-absorption and re-emission among energy-valleys with different energies of conduction bands. Our results draw attention to the spectral characteristics of nano-ribbon optical waveguides, which are as important as intensity to the stability and veracity of information transmission.