Structured illumination in total internal reflection fluorescence microscopy using a spatial light modulator

In wide-field fluorescence microscopy, illuminating the specimen with evanescent standing waves increases lateral resolution more than twofold. We report a versatile setup for standing-wave illumination in total internal reflection fluorescence microscopy. An adjustable diffraction grating written on a phase-only spatial light modulator controls the illumination field. Selecting appropriate diffraction orders and displaying a sheared (tilted) diffraction grating allows one to tune the penetration depth in very fine steps. The setup achieves 91 nm lateral resolution for green emission.     

A Simple Setup for Neutron Tomography at the Portuguese Nuclear Research Reactor

A simple setup for neutron radiography and tomography was recently installed at the Portuguese Research Reactor. The objective of this work was to determine the operational characteristics of the installed setup, namely the irradiation time to obtain the best dynamic range for individual images and the spatial resolution. The performance of the equipment was demonstrated by imaging a fragment of a seventeenth-century decorative tile.     

Experimental setup for studying the spectral-kinetic and space-dynamic characteristics of explosive decomposition of energetic materials

An experimental setup for studying spectral-kinetic and space-dynamic characteristics of explosion-induced luminescence from energetic materials is described. Explosion is initiated by nanosecond-and picosecond-wide electron and laser beams. Explosive luminescence of a single sample is detected in a spectral interval 450 nm wide with a spectral resolution of 2 nm and a spatial resolution of 50 μm. The time resolution, which is determined by a radiation source, is 30 ps.     

Aperture based Raman spectroscopy on SiGe film structures with high spatial resolution

We have investigated silicon–germanium (SiGe) line structures employing metallic apertures in combination with Raman spectroscopy to obtain high‐spatial strain resolution below the diffraction limit. The apertures were cut into specifically shaped electrochemically etched tungsten tips, which were adjusted within the Raman laser beam on the sample surface by a tuning fork atomic force microscope. With this setup, line structures on patterned SiGe films with a center‐to‐center distance down to 200 nm were resolved in the Raman scans, evidently indicating a resolution clearly below the far‐field Raman resolution of about 600 nm for the used instrument. This setup allows improved local strain analysis by Raman spectroscopy and shows potential for further near‐field Raman applications. Copyright © 2008 John Wiley & Sons, Ltd.     

Photothermal deflection microscopy for imaging sub-micronic defects in optical materials

Photothermal deflection is widely used to study defects in optical coatings and role of these defects in laser damage. Because defects responsible for laser damage are assumed to be nanometer-sized and lowly absorbing, both high spatial resolution and high sensitivity are required to detect them. In this work we theoretically and experimentally explore the capability of collinear photothermal deflection to give micronic resolution by reduction of the pump beam diameter. Thanks to a model describing temperature distribution and photothermal deflection, we have studied the effects of pump beam focusing on photothermal deflection. Then, we have developed a high resolution, high sensitivity microscope based on the photothermal deflection of a transmitted probe beam. The setup is characterized and the theoretical predictions are checked. We present a test of lateral spatial resolution obtained on specially prepared absorbing resolution targets and show that a lateral spatial resolution of 1 μm is reached on non-isolated defects. In case of single defects, we expect that 10 nm sized defects could be detected.     

Temperature analysis of laser heated polymers on microsecond time scales

To investigate the temperature profiles on laser heated polymer films, we track the thermal radiation with 1 μs time and 1 μm spatial resolution. The resulting two-dimensional temperature graphs are compared to finite element simulations in order to understand the heat conversion and flow. The temperature measurement setup consists of a NIR laser and an optical detection system, which includes high performance optics and a microsecond gated camera, equipped with several interference filters. In this way the thermal radiation is detected in the visible range with spectral resolution. Fitting the spectrum with Planck’s law, two-dimensional micrographs of the temperature distribution are obtained. For polystyrene surfaces we were able to analyze the heating and the ablation behavior. Good agreement was found between experimental results and finite element simulations, when ablation is limited to a few tens of nanometers of the film thickness. Ablation of polystyrene starts at 150°C, 50 K above the glass transition temperature. We suggest a photomechanical ablation mechanism at that threshold fluence. For ablation at higher fluence and peak temperature, experiments indicate a thermal decomposition reaction. The temperature range of spinodal decomposition is not reached and can in our case be ruled out as ablation mechanism.     

Pattern formation and direct measurement of the spatial resolution in a photorefractive liquid crystal light valve

In a photorefractive liquid crystal light valve, acting as a Kerr-like nonlinear optical medium, we show the appearance of optical patterns induced by a single mirror feedback. The spatial wavelength of the patterns scales with the distance between the mirror and the valve and the contrast of the patterns decreases for decreasing this distance. We use these properties to setup a new optical scheme for the measurement of the spatial resolution of the nonlinear device.     

基于CCD虚拟针孔探测的双轴共焦显微技术

双轴共焦显微技术具有独特的非共轴结构,与传统单轴共焦显微技术相比可利用较低数值孔径物镜实现较高的轴向分辨力,且具有工作距离大、信噪比高等优势。对基于CCD虚拟针孔(VPH)探测的双轴共焦显微成像系统的空间分辨特性进行了理论分析,并构建了相应的实验系统,对其轴向响应进行了实验验证。实验中照明物镜NAi=0.117,采集物镜NAc=0.106,θ=45°,得出系统轴向半高宽(FWHM)为2.63μm,比同等参数(NA=0.117)下单轴共焦显微系统的轴向FWHM高出约20倍。     

Two-point time-series measurements of minor-species concentrations in a turbulent nonpremixed flame

We report a technique that is capable of making simultaneous two-point time-series measurements of minor-species concentrations in turbulent flames. The experimental setup, which incorporates picosecond time-resolved laser-induced fluorescence, has a spatial resolution of less than 250 microm and a temporal resolution of less than 100 micros, which spatially and temporally resolve microscales in many turbulent flows. Two-point time-series data are given for a standard turbulent nonpremixed flame at Re= 10,000, including a discussion of potential implications.     

Full-field optical coherence microscopy

We present a new microscopy system for imaging in turbid media that is based on the spatial coherence gate principle and generates in parallel a complete two-dimensional head-on image without scanning. This system has been implemented in a commercial microscope and preserves the lateral resolution of the optics used. With a spatially incoherent source, speckle-free images with diffraction-limited resolution are recorded at successive depths with shot-noise-limited detection. The setup comprises a photoelastic modulator for path difference modulation and a two-dimensional CCD array and uses a multiplexed lock-in detection scheme.     

采用光纤和YAP晶体的小型γ相机的蒙特卡罗模拟

基于波长位移光纤(WSF)耦合YAP晶体中的光子传输特性,用GEANT4软件包建立了一个蒙特卡罗模拟程序.对采用波长位移光纤耦合平板式YAP晶体的小型单管γ相机的性能进行了计算机模拟.采用波长位移光纤耦合光电倍增管光阴极面的读出方式,和晶体直接耦合光电倍增管光阴极面相比,在相同的晶体面积大小条件下,PSPMT光阴极面积可大大缩小,使费用降低.模拟结果表明：γ射线与晶体发生作用的地方所对应的光纤输出的平均光子数最少为15个,位置灵敏光电倍增管完全可以探测到.说明采用闪烁晶体－WSF－位置灵敏光电倍增管的读出方式是可行的;在用硅油耦合波长位移光纤和YAP晶体的情况下,获得的空间分辨率为1.28 mm(FWHM).模拟结果也说明了增加平均光子数对提高空间分辨率的重要性.     

In situ spatial-profile monitoring of beam flux of neutral free radicals produced by photo-deionization of negative ion beams

Ion-current difference measurement by light intensity modulation (ICD) is introduced as a convenient method to characterize a purified beam of momentum-controlled neutral free radicals produced by photo-deionization of a negative ion beam for the purpose of surface-reaction-selective device processing. The ICD setup developed in this study to estimate the number flux of the photo-deionized neutral particles exhibited the high precision, sensitivity, and spatial resolution.     

Waveguide-based off-axis holography with hard X rays

We present an off-axis holography experiment based on the coherent cone beams emitted from a pair of x-ray waveguides. A magnified off-axis hologram is recorded, from which the phase of the optical transmission function of a sample is obtained by digital holographic reconstruction. A spatial resolution of about 100 nm has been achieved at 10.4 keV photon energy. Spatial resolution is determined by the cross-sectional dimensions of the waveguide and could approach a fundamental limit of about 10 nm in future experiments. In addition, we propose a new experimental setup that might overcome this limitation.     

Resolution of ghost imaging with entangled photons for different types of momentum correlation

We present an analytical analysis of the spatial resolution of quantum ghost imaging implemented by entangled photons from a general, spontaneously parametric, down-conversion process. We find that the resolution is affected by both the pump beam waist and the nonlinear crystal length. Hence, we determined a method to improve the resolution for a certain imaging setup. It should be noted that the resolution is not uniquely related to the degree of entanglement of the photon pair since the resolution can be optimized for a certain degree of entanglement. For certain types of Einstein-Podolsky-Rosen(EPR) states——namely the momentum-correlated or momentum-positively correlated states——the resolution exhibits a simpler relationship with the pump beam waist and crystal length. Further, a vivid numerical simulation of ghost imaging is presented for different types of EPR states,which supports our analysis. This work discusses applicable references to the applications of quantum ghost imaging.     

优化X射线同轴相位衬度成像的理论研究

采用同轴相位衬度成像方法,基于PGW理论获得的频域相位衬度传递函数,对于理想光源和多色X射线源,用计算机模拟分析了如何选择物像距离和空间频率以获取最佳相位衬度像。实际应用中要综合考虑具体成像实验装置对于物像距离的可调范围以及成像分辨率的要求。对于具有一定谱宽的X射线源,应选择谱宽尽量小的源,以获得含信息量丰富、分辨率高的图像。     

Real-time optical imaging and tracking of micron-sized particles

We report real-time imaging and dynamics monitoring of micrometer predefined and random sized particles by time-space-wavelength mapping technology using a single-detector. Experimentally, we demonstrate real-time line imaging of a 5 μm polystyrene microsphere, glass powder particles and patterns such as fingerprints with up to 5 μm resolution at 1 line/50 ns capture rate. By using the same setup, real-time displacement tracking of micrometer-size glass particles with 50 ns temporal resolution and up to 5 μm spatial resolution is achieved. We also show that existing correlation spectroscopy algorithms can be adopted to extract dynamic information in a complex environment.     

近场头相关传输函数的测量与分析

设计了测量距离可调整的头相关传输函数的实验测量方法，并采用人工头进行近场头相关传输函数的测量，建立了高空间分辨率的近场头相关传输函数数据库，为进一步开展双耳听觉的研究和虚拟听觉的应用提供了数据基础。根据实验数据，初步分析了远、近场情况下，距离、仰角、方位角等参量对头相关传输函数的影响规律。     

Versatility of a hard X‐ray Kirkpatrick–Baez focus characterized by ptychography

In the past decade Kirkpatrick–Baez (KB) mirrors have been established as powerful focusing systems in hard X‐ray microscopy applications. Here a ptychographic characterization of the KB focus in the dedicated nano‐imaging setup GINIX (Göttingen Instrument for Nano‐Imaging with X‐rays) at the P10 coherence beamline of the PETRA III synchrotron at HASLYLAB/DESY, Germany, is reported. More specifically, it is shown how aberrations in the KB beam, caused by imperfections in the height profile of the focusing mirrors, can be eliminated using a pinhole as a spatial filter near the focal plane. A combination of different pinhole sizes and illumination conditions of the KB setup makes the prepared optical setup well suited not only for high‐resolution ptychographic coherent X‐ray diffractive imaging but also for moderate‐resolution/large‐field‐of‐view propagation imaging in the divergent KB beam.     

SIL-based confocal fluorescence microscope for investigating individual nanostructures

We developed a fluorescence confocal microscope equipped with a hemispherical solid immersion lens (SIL) and apply it to study the optical properties of light-harvesting complexes. We demonstrate that the collection efficiency of the SIL-equipped microscope is significantly improved, as is the spatial resolution, which reaches 600 nm. This experimental setup is suitable for detailed studies of physical phenomena in hybrid nanostructures. In particular, we compare the results of fluorescence intensity measurements for a light-harvesting peridinin-chlorophyll-protein (PCP) complex with and without the SIL.     

Fast X‐ray microfluorescence imaging with submicrometer‐resolution integrating a Maia detector at beamline P06 at PETRA III

The high brilliance of third‐generation synchrotron sources increases the demand for faster detectors to utilize the available flux. The Maia detector is an advanced imaging scheme for energy‐dispersive detection realising dwell times per image‐pixel as low as 50 µs and count rates higher than 10 × 10⁶ s^?1. In this article the integration of such a Maia detector in the Microprobe setup of beamline P06 at the storage ring PETRA III at the Deutsches Elektronen‐Synchrotron (DESY) in Hamburg, Germany, is described. The analytical performance of the complete system in terms of rate‐dependent energy resolution, scanning‐speed‐dependent spatial resolution and lower limits of detection is characterized. The potential of the Maia‐based setup is demonstrated by key applications from materials science and chemistry, as well as environmental science with geological applications and biological questions that have been investigated at the P06 beamline.