原子力与光子扫描隧道组合显微镜

介绍了超高分辨光于扫描隧遭显微镜（PSTM）的计冗历程,为解决第一代（单光束照明）光千扫捕隧逼显傲镜中存在人为假象和样品光学图像与形貌图像难于分离两个难题,用“对称双光束照明方法消假象,用原子力与光子扫描隧道组合显微镜（AF／PSTM）图像分解方法分离样品光学透过率、折射率与形貌图像。研制成功新一代原子力与光子扫描隧道组合显微镜（AF／PSTM）样机。该样机在一次扫描中已获得两幅原子力显微镜图像（形貌与相位）和两幅光学图像（透过率和折射率）,有效地减少了假象,分解了样品光学折射率、透过率与形貌图像。     

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     

基于迈克耳孙干涉仪的近场光学实验

介绍了一种以迈克耳孙干涉仪作为操作平台的近场光学实验系统.该系统可以测量棱镜内表面全内反射产生的隐失场,观察两维光栅样品的近场光学结构,还可以用于光子扫描隧穿显微镜(PSTM)的原理性实验,有助于学生深入了解隐失场的结构和近场光学显微镜的基本工作原理.该装置具有结构简单可靠,操作简便等特点,十分适用于物理实验教学.     

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.     

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.     

用于原子力与光子扫描隧道组合显微镜的浸油显微物镜

双功能原子力与光子扫描隧道显微镜（AF／PSTM）用π对称双光束照明方法来消除假象。为改进现有的AF／PSTM系统,提出新的照明系统方案,并设计了新方案中需要的高数值孔径的浸油显微物镜。根据具体的物镜系统参数要求,选择合适的初始结构,用ZEMAX光学设计软件对物镜进行设计、优化和像质评价,设计结果显示浸油物镜的数值孔径大约1.54,可以很好地满足照明系统的需要。     

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.     

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.     

SFM/SNOM结合的扫描探测显微镜

采用光纤探针的扫描近场光学显微镜 (SNOM)存在某些弱点 ,如探针特别脆 ,不易贴近样品表面扫描 ,探针的转输效率低等。近年来发展了将SFM /SNOM结合起来的扫描探测显微镜。利用微加工工艺技术 ,将小孔集成在悬臂探针中 ,使探针既能批量制备 ,又具有很好的重复性。探针悬臂在垂直于样品表面方向上的弹性常数较小 ,针尖不易损坏。在接触模式中利用这种SFM /SNOM组合探针可将样品的形貌像、摩擦力和光学透射像等信息同时记录下来。对于综合研究样品表面的介观性质十分有利。     

Sensitivity analysis of scanning near-field optical microscope probe

In this paper, we study the dynamic modes of a scanning near-field optical microscope (SNOM) which uses an optical fiber probe; and the sensitivity of flexural and axial vibration modes for the probe were derived and the closed-form expressions were obtained. According to the analysis, as expected each mode has a different sensitivity and the first mode is the most sensitive mode of flexural and axial vibration for the SNOM probe. The sensitivities of both flexural and axial modes are greater for a material surface that is compliant with the cantilever probe. As the contact stiffness increases, the high-order vibration modes are more sensitive than the lower-order modes. Furthermore, the axial contact stiffness has a significant effect on the sensitivity of the SNOM probe, and this should be noted when designing new cantilever probes.     

Theoretical study of broadband near-field optical spectrum of twisted bilayer graphene

We theoretically study the broadband near-field optical spectrum of twisted bilayer graphene (TBG) at various twist angles near the magic angle using two different models. The spectrum at low Fermi energy is characterized by a series of peaks that are almost at the same energies as the peaks in the far-field optical conductivity of TBG. When the Fermi energy is near a van Hove singularity, an additional strong peak appears at finite energy in the near-field spectrum, which has no counterpart in the optical conductivity. Based on a detailed calculation of the plasmon dispersion, we show that these spectroscopic features are associated with interband and intraband plasmons, which can provide critical information about the local band structure and plasmonic excitations in TBG. The near-field peaks evolve systematically with the twist angle, so they can serve as fingerprints for identifying the spatial dependent twist angle in TBG samples. Our findings pave the way for future experimental studies of the novel optical properties of TBG in the nanoscale.     

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.     

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。     

光子扫描隧道显微镜球形样品二维近场强度分析

采用时域有限差分方法计算全内反射和光子扫描隧道显微镜系统。光子扫描隧道显微镜的基本工作原理是隐失波的产生和探测，当入射光在两种介质的分界面上发生全内反射，并在界面处产生非辐射的电磁波——隐失波时，采取对两界面入射光进行分别设置的方法即“三波法”设置入射激励元。分别计算一个球和两个球形样品的近场分布，并计算散射小球为探针，一个球为样品的扫描图像。结果表明：采用二维时域有限差分方法计算能较直观地显示样品表面的近场分布。表明时域有限差分方法在光子扫描隧道显微镜理论研究中具有很大潜力。     

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.     

高效、高分辨光纤微探针的制备及检验

提出两种同时满足高分辨、高传光效率的探针模型以及制备方法 :先用自制热拉装置将光纤拉制成过渡区为双曲线或抛物线形的探针 ,然后用 4 0 %氢氟酸进行快速腐蚀 ,使探针孔径变小而保持过渡区域形状和锥度基本不变。所获探针孔径变化范围为 2 0～ 2 0 0 nm,锥度 2 0°～ 6 0°。为检验探针性能 ,将两种探针的出射光分布与用传统热拉法所得到探针进行对比 ;探测了光子扫描隧道显微镜状态下的倏逝波衰减曲线 ;给出了用集光式扫描近场光学显微镜得到的近场光学图像 ;同时 ,验证了探针对剪切力控制的适用性。     

Optical waveguide behavior of Se-doped and undoped CdS one-dimensional nanostructures using near-field optical microscopy

The optical waveguide behaviors of CdS and CdS _x Se_1−x nanostructures are studied using near-field optical microscopy. Optical measurements demonstrate that light may be guided on sub-wavelength scales along CdS nanoribbons in straight or bent structures. The photoluminescence (PL) spectra from nanoribbon emission using scanning near-field optical microscopy are analyzed under different incident laser intensities. The PL spectra along Se-doped and undoped CdS nanoribbons at different propagation distances are investigated. Both the guided PL spectra of Se-doped and undoped CdS nanoribbons show red-shifts because of the band-edge absorption. Our results are useful for the development of new kinds of functional nano devices. Supported by the National Natural Science Foundation of China (Grant Nos. 10574002, 90406007, and 50602015) and the National Basic Research Program of China (Grant No. 2007CB936800)     

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.     

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.