我国研制成功超分辨成像系统

<正>中科院沈阳自动化研究所的研究人员研发出具有实时视觉反馈能力的扫描微透镜超分辨成像技术,这种新技术可在自然条件下打破光学衍射定律所限制的观测极限,实现生命和非生命样品的超分辨实时观测,让纳米机器人的眼睛更     

双胶合透镜的三维成像研究

应用标量衍射理论分析了双胶合透镜的三维超分辨成像特性。对于所设计的双胶合透镜,数值模拟表明,焦平面上主瓣的强度是第1旁瓣的57.14倍,是单一个透镜主瓣强度的2.25倍,而主瓣的半径则是单一个透镜的0.49倍;轴线方向上,主瓣与第1旁瓣的强度之比与单一个透镜的基本相同,但是双胶合透镜的焦深则比单一个透镜的小0.25倍。说明双胶合透镜在横向和轴向同时具有较强的超分辨能力。通过与加圆环光瞳或加相位光瞳的方法比较发现,双胶合透镜具有较好的三维成像能力,可以作为共焦3-D成像和近场光学记录的理想光学器件。     

新型光子纳米射流器件的设计

光子纳米射流是一种高强度,极窄的亚波长电磁场区域,它是由介电微球或微柱体的Mie散射对电磁场的聚焦作用产生的。光子纳米射流广泛应用于激光加工、纳米光刻、光学高密度存储以及超分辨率显微镜。从径向偏振光的角度出发,使用一种介电圆环结构对光束进行聚焦,由于径向偏振光在焦点区域可以产生较强的纵向场,通过优化圆环的尺寸、折射率以及与物镜焦点的相对位置,可以得到超过90%光束质量的纵向光子纳米射流,而且强度相比于未使用圆环时可以提高约一个数量级,并在高折射率下可以获得半高全宽小于衍射极限尺寸的光斑,因此该结构预计可以在粒子加速、光镊以及拉曼光谱学中有所应用。     

激光棒干涉测量中单双通法的对比

由于激光棒具有细长的特殊形貌特征,传统的双通测试方法虽然灵敏度较高,但是往往存在明显的衍射效应和多重成像导致的边缘黑环,这会导致有效测量面积的缩减,对于小口径光学元件的测量尤为不利。为了克服这一缺陷,采用单通法测量激光棒的波前畸变,使用直角棱镜作为反射件,使得测试光仅通过激光棒一次,从而减少光路中的等效圆孔数和成像次数,抑制衍射和边缘重叠。利用展开的多小孔模型讨论了衍射效应的影响,并且从成像角度讨论边缘重叠的成因,从而得出单通法的优势。另外,为使参考光与测试光的匹配,需要将直角棱镜旋转至少5.40°偏摆角以提高干涉条纹的对比度。最终测得激光棒波前畸变的峰谷值为0.068λ,均方根值为0.012λ。     

宽范围高对准精度纳米压印样机的研制

传统的光学光刻技术由于受光波波长和数值孔径等因素的限制难于制作特征尺度小于100nm的图案.与传统光刻相比,纳米压印光刻的分辨率不受光的衍射和散射等因素的限制,可突破传统光刻工艺的分辨率极限,因而被认为是一种获得100nm以下图案较好的下一代方法.介绍了自行研制的具有高定位和对准精度的纳米压印样机.利用该样机压印出的纳米级光栅、微凸点阵列、微透镜阵列等纳米结构和微器件的图形质量均匀性良好.该工艺为实现低成本、大批量复制纳米结构创造了条件,在半导体集成电路、微光学、生物和化学分析等微纳结构和器件的制作中有着广泛的应用前景.     

实验产生超分辨光学聚焦暗斑

用二元相位器件调制角向偏振激光光束,然后用高数值孔径物镜聚焦,在实验上产生了一个超分辨光学聚焦暗斑。二元相位器件的调制作用是通过让角向偏振光束经一块刻有多环同心环状凹槽的玻璃基板实现的。用刀口法检测了焦点附近的3D光束分布特性,得到了尺寸是0.32λ且在4λ左右的长度内保持不变的超分辨暗斑。这样的光学聚焦暗斑可能会应用于超分辨显微技术和光学捕获。     

面向超分辨光学成像的浸没微球透镜控制

微球透镜配合传统光学显微镜可以采集到衍射极限以下的超分辨光学图像,为了精确控制微球透镜在样品表面的位置,同时扩大超分辨成像范围,提出了一种控制微球透镜的方法,结合多轴微动平台实现微球透镜的精确定位与成像扫描操作。通过光学仿真分析了微球透镜超分辨成像效果,并对精密微动平台进行了运动学分析。为了提高超分辨成像效果,将微球透镜浸没于液体介质中,并对在液体中运动的微球透镜进行力学分析。通过实验,清晰分辨出130nm(~λ/4)的蓝光光碟条纹间隙,证明了微球透镜具有超分辨成像能力,结果表明,微球透镜可以在传统光学显微镜的基础上进一步提高约3.52倍的放大倍数。通过控制微球透镜以5×10~(-6) m/s的速度在液体中按"S"型轨迹移动,实现了对一个视场内样品的超分辨成像,此控制方法可以精确控制微球透镜的运动,通过扫描的方式可以扩大微球透镜的观测范围,提高观测速度。     

近场光学显微镜

近场光学显微镜根据非辐射场的探测与成像原理,能够突破普通光学显微镜所受到的衍射极限,在超高光学分辨率下进行纳米尺度光学成像与纳米尺度光谱研究,本文简介近场光学的基本原理与近场光学显微镜的仪器发展;讨论近年来近扬光学显微镜的一些进展,接近原子分辨的超高分辨率光学成像,近场光谱与半导体量子器件,生命科学中超显微观察和近场荧光以及近场原理在产业化中的应用。     

全孔径背向散射诊断光学系统

基于新的激光聚变驱动装置的需要,设计了全孔径背向散射诊断光学系统并介绍了光学设计中涉及的若干关键技术。采用低反射率的楔形反射镜衰减背向散射光能量,降低后继元件对光学薄膜损伤阈值的要求。通过缩束镜缩小光束口径,减小光学元件尺寸;同时采取折叠光路结构来缩小系统体积。对空间滤波器和光学滤片进行组合,屏蔽了打靶倍频光干扰及不同散射类型的相互串扰。采用光学白板对色散严重的背向散射光进行漫反射匀化,使光谱测量系统获得完整的光谱信息。最后,选取抛物面为空间分布成像目标面,通过分析空间分布成像光束的结构设计了成像镜头。设计的诊断光学系统具有散射时间测量、光谱测量、空间分布成像、能量测量等功能,光学测量模块尺寸为1.9m×0.9m×1.5m。该全孔径背向散射诊断光学系统在新的激光聚变驱动装置中具有潜在的应用价值。     

光学功率谱式柱形颗粒测径仪的研究

本文实现了用光学功率谱技术对柱形颗粒尺寸分布的测量。文中以柱形颗粒衍射理论为基础，建立了与光束相垂直的平面内长度方向可随机取向的柱形颗粒群衍射的光学功率谱分布模型，并用环形光电探测器接收和累加多个随机取向的一维衍射光能。     

Online monitoring of gold nanoparticles and induced aggregation by photothermal lens microscopy

In this paper, we have developed inverted photothermal lens microscopy (PTLM) with a flow through optical cell for online detection of gold nanoparticles (AuNPs) to monitor the AuNP production process and aggregation. The indirect detection of the plasmonic signals of AuNPs was performed using the thermal lens phenomena. The measurements were made using continuous-wave excitation (532?nm) and probe laser beams (652?nm). The changes of the transmitted probe beam’s intensity were detected with a photodiode. The results show the possibility of online determination of AuNPs in micro and nanovolumes in the range of 1.7–13.7 particles for the focal volume of the excitation beam. The obtained limit of detection and relative standard deviation for 10 repeated measurements of AuNPs were 0.65?nM and 1.43%, respectively. Therefore, this system was successfully applied for screening of aggregation in process applications.     

Optical microscopy with improved resolution using two-beam interference of low-coherence light

In recent years, high-resolution microscopy using structured illumination has been practically applied for fluorescent bio-imaging. However, there is a large amount of speckle noise in reflected- and scattered-light images, because structured illumination is typically generated by laser-beam interference. Hence, this high-resolution imaging technique cannot be effectively used in industrial applications. In this study, we attempted to generate structured illumination using two-beam interference of low-coherence light for high-resolution and low-speckle imaging. First, we constructed an optical system consisting of a Michelson interferometer configured in such a manner that it achieved zero optical path-length difference and allowed the interference fringes to be manipulated. Then, we confirmed that the generated structured illumination width corresponded to the coherence length of the light source. As a final result of the resolution improvement experiment, the narrow sample pitch of 0.4 μm was successfully resolved beyond the diffraction limit of 0.74 μm with relatively less speckle noise.     

Pushing the resolution limits in cryo electron tomography of biological structures

Cryo electron tomography is a three-dimensional imaging technique that is suitable for imaging snapshots of the structural arrangements of biomolecular complexes and macromolecules, both in vitro and in the context of the cell. In terms of attainable resolution, cryo electron tomographic reconstructions now show resolvable details in the 5-10 nm range, connecting optical microscopy with molecular imaging techniques. In view of the current developments in super-resolution light microscopy and correlative light and electron microscopy, cryo electron tomography will be increasingly important in structural biology as a tool to bridge light microscopy with molecular imaging techniques like NMR, X-ray diffraction and single particle electron microscopy. In cell biology, one goal, often referred to as visual proteomics, is the molecular mapping of whole cells. To achieve this goal and link cryo electron tomography to these high-resolution techniques, increasing the attainable resolution to 2-5 nm is vital. Here, we provide an overview of technical factors that limit the resolution in cryo electron tomography and discuss how during data acquisition and image processing these can be optimized to attain the highest possible resolution. Also, existing resolution measurement approaches and current technological developments that potentially increase the resolution in cryo electron tomography are discussed.     

Medical Imaging Techniques Combining Light and Ultrasound

The combination of light and ultrasound can lead to new medical imaging techniques combining the spectroscopic capability of light with the spatial resolution of ultrasound. Spectroscopy can be used to measure blood volume and blood oxygen, but because most biological tissues are highly scattering at optical wavelengths, spatial resolution is poor. Ultrasound provides excellent resolution, but not good soft-tissue contrast. There are many techniques for combining light and ultrasound, but the two discussed in this paper have emerged as having the most promise for medical applications. In the first, optoacoustic imaging, an acoustic pulse is generated by a pulse of laser light, and the detected sound is used to produce an image. In the second, acousto-photonic imaging, ultrasound modulates laser light used for diffusive optical tomography. Both of these techniques show promise for a variety of medical applications.     

A simple model of holography and some enhanced resolution methods in electron microscopy

A simple pictorial model of electron interference effects based on an extended representation of the autocorrelation function is described and developed. Unlike Abbe's theory of transmission imaging, the model incorporates fully the effect of the loss of phase that occurs in the detector plane. The aperture transfer function and information limit (envelope function) are also incorporated with reference to the simplest scattering geometry of Young's slits. The model is then applied to holography, the diffraction phase problem, ptychography, Wigner distribution deconvolution, conventional bright-field imaging, single side-band imaging and tilt-series reconstruction. Some of these methods require an understanding of four-dimensional integral functions, but the model reduces the problem into a projection of a two-dimensional space. It is hoped that the model will help material scientists who are not specialists in imaging and diffraction theory to understand some recent developments in advanced super-resolution imaging methods.     

Novel in situ setup to study the formation of nanoparticles in the gas phase by small angle x-ray scattering

An in-house built aerosol generator setup for in situ gas phase studies of aerosol and nanoparticles is described. The aerosol generator with an ultrasonic ceramic disk mist maker provides high enough particle concentrations for structural gas phase analysis by synchrotron small angle x-ray scattering (for water approximately 4 x 10(8) droplets/s with a droplet size of approximately 2.5 microm). The working principle was proved by scattering of gold nanoparticles. For evaporation induced self-assembly studies of nanostructured particles, an additional thermal treatment chamber was included in the setup. The first on-line gas phase data with our setup for mesostructured silica particles are presented for different thermal treatments. Scanning electron microscope imaging revealed the average particle size to be approximately 1 microm. Furthermore, to quantify their internal nanostructure, diffraction experiments of deposited silica aerosols were carried out and the corresponding electron density map indicates a silica wall thickness of about 1 nm.     

In situ multipurpose time-resolved spectrometer for monitoring nanoparticle generation in a high-pressure fluid

We developed a multipurpose time-resolved spectrometer for studying the dynamics of nanoparticles generated by pulsed-laser ablation (PLA) in a high-pressure fluid. The apparatus consists of a high-pressure optical cell and three spectrometers for in situ measurements. The optical cell was designed for experiments at temperatures up to 400 K and pressures up to 30 MPa with fluctuations within ±0.1% h(-1). The three spectrometers were used for the following in situ measurements at high pressures: (i) transient absorption spectrum measurements from 350 to 850 nm to investigate the dynamics of nanoparticle generation from nanoseconds to milliseconds after laser irradiation, (ii) absorption spectrum measurements from 220 to 900 nm to observe the time evolution of nanoparticles from seconds to hours after laser ablation, and (iii) dynamic light scattering measurements to track nanoparticles with sizes from 10 nm to 10 μm in the time range from seconds to hours after laser ablation. By combining these three spectrometers, we demonstrate in situ measurements of gold nanoparticles generated by PLA in supercritical fluids. This is the first report of in situ time-resolved measurements of the dynamics of nanoparticles generated in a supercritical fluid.     

Quantifying the structural integrity of nanorod arrays

Arrays of aligned nanorods oriented perpendicular to a support, which are accessible by top‐down lithography or by means of shape‐defining hard templates, have received increasing interest as sensor components, components for nanophotonics and nanoelectronics, substrates for tissue engineering, surfaces having specific adhesive or antiadhesive properties and as surfaces with customized wettability. Agglomeration of the nanorods deteriorates the performance of components based on nanorod arrays. A comprehensive body of literature deals with mechanical failure mechanisms of nanorods and design criteria for mechanically stable nanorod arrays. However, the structural integrity of nanorod arrays is commonly evaluated only visually and qualitatively. We use real‐space analysis of microscopic images to quantify the fraction of condensed nanorods in nanorod arrays. We suggest the number of array elements apparent in the micrographs divided by the number of array elements a defect‐free array would contain in the same area, referred to as integrity fraction, as a measure of structural array integrity. Reproducible procedures to determine the imaged number of array elements are introduced. Thus, quantitative comparisons of different nanorod arrays, or of one nanorod array at different stages of its use, are possible. Structural integrities of identical nanorod arrays differing only in the length of the nanorods are exemplarily analysed.     

A protocol for single-source dual-pulse stimulated emission depletion setup with Bessel modulation

STimulated Emission Depletion (STED) microscopy attains super-resolution in biological imaging beyond the diffraction limit. Here, we give a concise protocol to construct a dual-pulse STED setup with one super-continuum laser. Moreover, a flexible and dismountable Bessel modulation module is introduced for potential 2D-stack STED imaging. Experiments and notices are introduced in detail, with discussion on some important check-points for STED, such as detector saturation. Finally, the results validate the system working.