拼接干涉技术在同步辐射领域的发展现状及趋势

针对同步辐射领域光学元件的口径逐渐增大,其面形测量精度的要求已达到纳弧度级的问题,本文研究了该领域先进的面形测量方法——拼接干涉技术,以实现光学元件的高分辨率二维测量。介绍了拼接干涉技术的基本原理,综述了目前同步辐射光学领域常用的面形测量设备——激光光束长程面形仪、高精度自准直纳米测量仪,以及拼接干涉仪的发展历程和特点,比较了它们各自的缺点和优势。最后,分析了拼接干涉涉及的主要误差来源,指出该技术的应用和发展趋势主要有拼接算法的创新,干涉仪测量的快速化,拼接干涉仪的商业化,以及拼接干涉技术与其他科学技术的融合等。     

Diffractive focusing fan-out element for the parallel DNA sequencer

Various issues of creation of diffractive optical elements transforming one laser beam with small divergence to a matrix of converging beams with a diffraction size of focused spots in the plane of object illumination and their application for problems of DNA sequencing and microscopy are considered. The parameters of diffractive elements are calculated and optimized in the approximation of the Fresnel–Kirchhoff diffraction theory. Diffractive elements are fabricated by the method of direct laser writing on a photoresist by using a circular laser writing system. Experimental characteristics of a diffractive element creating a matrix consisting of 33 × 33 beams, which are focused in one plane at a distance of 210 mm, are presented. The degree of nonuniformity of beam intensities determined by the ratio of beam intensities in the central region to intensities of peripheral beams is 1/2.5, which is potentially sufficient to be used in DNA sequencing problems. The maximum distortions of spot positions in the entire focusing field is <0.15%.     

激光聚变冲击波被动式测速光学系统设计

针对激光聚变装置冲击波速度被动测量的需求,设计了一种测速光学系统。采用高紫外透过率的氟化玻璃,实现了透射式300～800nm复消色差设计。系统光路具有前后两组镜头,中间为平行光,镜头间距可变,光路适应能力强。系统前端两侧的双目机器视觉能够完成自动寻的。平行光路中设置5个激光器,轴上的1个前向照明靶点用来观察条纹相机狭缝处的目标像质,轴外的4个与光轴平行后向传输用来标识系统光轴的位置,激光器部件可电动切入/切出。系统前组镜头F/#数为4,宽谱工作物方分辨率优于10μm,532nm单波长工作物方分辨优于5μm。该光学系统光路排布灵活,可单独被动测速,也可与主动测速系统VISAR耦合构成主被一体复合测速系统,满足激光聚变装置冲击波测速的需求。     

High-resolution constant-height imaging with apertured silicon cantilever probes

We present high-resolution aperture probes based on non-contact silicon atomic force microscopy (AFM) cantilevers for simultaneous AFM and near-infrared scanning near-field optical microscopy (SNOM). For use in near-field optical microscopy, conventional AFM cantilevers are modified by covering their tip side with an opaque aluminium layer. To fabricate an aperture, this metal layer is opened at the end of the polyhedral probe using focused ion beams (FIB). Here we show that apertures of less than 50 nm can be obtained using this technique, which actually yield a resolution of about 50 nm, corresponding to λ/20 at the wavelength used. To exclude artefacts induced by distance control, we work in constant-height mode. Our attention is particularly focused on the distance dependence of resolution and to the influence of slight cantilever bending on the optical images when scanning at such low scan heights, where first small attractive forces exerted on the cantilever become detectable.     

基于VC++的纳米分辨远场光学共焦成像系统的扫描控制

为降低纳米分辨远场光学共焦成像系统的出错率和提高此系统的实验效率,设计了纳米分辨远场光学共焦成像系统的扫描控制子系统。纳米分辨远场光学共焦成像系统的主要组成器件为纳米移动平台,被测物体置于此平台上随平台移动而运动。如何使被测物体作有规律的运动是实验能否成功的关键。采用VC++开发平台设计的扫描自动控制子系统即为解决这一问题而开发。子系统使用方便、界面友好。     

Are electron tweezers possible?

Positively answering the question in the title, we demonstrate in this work single electron beam trapping and steering of 20–300 nm solid Al nanoparticles generated inside opaque submicron-sized molten Al–Si eutectic alloy spheres. Imaging of solid nanoparticles and liquid alloy in real time was performed using energy filtering in an analytical transmission electron microscope (TEM). Energy-filtering TEM combined with valence electron energy-loss spectroscopy enabled us to investigate in situ nanoscale transformations of the internal structure, temperature dependence of plasmon losses, and local electronic and optical properties under melting and crystallization of individual binary alloy particles. For particles below 20 nm in size, enhanced vibrations of the dynamic solid–liquid interface due to instabilities near the critical threshold were observed just before melting. The obtained results indicate that focused electron beams can act as a tool for manipulation of metal nanoparticles by transferring linear and angular mechanical momenta. Such thermally assisted electron tweezers can be utilized for touchless manipulation and processing of individual nano-objects and potentially for fabrication of assembled nanodevices with atomic level sensitivity and lateral resolution provided by modern electron optical systems. This is by three orders of magnitude better than for light microscopy utilized in conventional optical tweezers. New research directions and potential applications of trapping and tracking of nano-objects by focused electron beams are outlined.     

Multibeam laser writing of diffractive optical elements

A new version of the method of direct multibeam laser writing of diffractive optical elements (DOE) is proposed and investigated. A writing area in the form of an array of focused light spots is formed by splitting the writing laser beam into multiple beams by using a Dammann grating and focusing of these beams in the plane of a moving carrier with a photosensitive material. Adjustment of the radial pitch of writing and correction of the uniformity of the beam intensity is carried out by tilting the Dammann grating and displacing it in the dispersion direction. In writing DOEs, the radial pitch of discrete displacement of the writing area with respect to the plane of the DOE is set equal to or multiple of the average radial distance between the radial projections of the centers of the focused light spots. This version provides improved performance and accuracy due to high-quality paralleling of the writing beam and the averaging effect in superimposed writing.     

High-resolution interference methods of inspecting the surface and layered structure profile of precision engineering and instrument-making products

The methods of interference measurements using focused laser and nonlaser optical probing beams and microscopic systems for measuring surface microprofile parameters and parameters of a layered microstructure of transparent and scattering objects are considered. High-coherence (laser) and low-coherence interferometry techniques are analyzed and their comparative analysis as applied to practical applications for inspection purposes in high-tech production processes and for the development and adjustment of novel engineering methods of the development of new designs and materials is performed.     

A subnanosecond pulsed ion source for micrometer focused ion beams

A new, compact design of an ion source delivers nanosecond pulsed ion beams with low emittance, which can be focused to micrometer size. By using a high-power, 25 fs laser pulse focused into a gas region of 10(-6) mbar, ions at very low temperatures are produced in the small laser focal volume of 5 mum diameter by 20 mum length through multiphoton ionization. These ions are created in a cold environment, not in a hot plasma, and, since the ionization process itself does not significantly heat them, have as a result essentially room temperature. The generated ion pulse, up to several thousand ions per pulse, is extracted from the source volume with ion optical elements that have been carefully designed by simulation calculations. Externally triggered, its subnanosecond duration and even smaller time jitter allow it to be superimposed with other pulsed particle or laser beams. It therefore can be combined with any type of collision experiment where the size and the time structure of the projectile beam crucially affect the achievable experimental resolution.     

3D reconstruction of high-resolution STED microscope images

Tackling biological problems often involves the imaging and localization of cellular structures on the nanometer scale. Although optical super-resolution below 100 nm can be readily attained with stimulated emission depletion (STED) and photoswitching microscopy methods, attaining an axial resolution <100 nm with focused light generally required the use of two lenses in a 4Pi configuration or exceptionally bright photochromic fluorophores. Here, we describe a simple technical solution for 3D nanoscopy of fixed samples: biological specimens are fluorescently labeled, embedded in a polymer resin, cut into thin sections, and then imaged via STED microscopy with nanoscale resolution. This approach allows a 3D image reconstruction with a resolution <80 nm in all directions using available state-of-the art STED microscopes.     

Applications of focused ion beams

A finely focused ion beam system is described. Beams of Ga, In, and Au ions emitted from a liquid metal ion source are routinely focused to spot diameters of ∼0.1 to 3.0 μm at a current density of ∼0.5 A/cm² and a beam energy of 20 keV. Focused beams with energies of 1 to 30 keV have also been produced. Three applications are discussed: (1) scanning ion microscopy, (2) mask repair, and (3) ion beam lithography. Scanning ion images illustrating topographic and chemical contrast are presented. The repair of opaque and clear defects in optical masks, and opaque defects in X-ray masks is shown.Defects are imaged with the ion beam and removed by sputter erosion. Edge reconstruction of 0.5 μm features is demonstrated. Most repairs take less than 10 s/μm². The advantages and limitations of ion beams for lithography are discussed.     

Super-resolution bright-field optical microscopy based on nanometer topographic contrast

By using an expectation-maximization maximum likelihood estimation algorithm to improve the lateral resolution of a recently developed non-interferometric wide-field optical profilometer, we obtain super-resolution bright-field optical images of nanometer features on a flat surface. The optical profilometer employs a 365-nm light source and an ordinary objective lens of a 0.95 numerical aperture. For objects of 100 nm thickness, lateral features about lambda/7 can be resolved in the restored images without fluorescence labeling. Current image acquisition rate is 0.1 frame/sec, which is limited by the brightness of the light source. With a brighter light source, the imaging speed can be fast enough for real-time observation of dynamic activities in the nanometer scale.     

Comparison of the energy characteristics of tightly focused needle beams with longitudinal polarization

A comparative analysis is made of spatial variations in the energy characteristics of tightly focused, longitudinally polarized needle laser beams generated by an optical system with selective thin-film linear-to-radial polarization conversion, followed by their spatial filtering and tightannular focusing to subwavelength sizes. For the important special case of ideal radial polarization of a focused beam, longitudinal cross-sections of spatial distributions of the electric energy density and the Poynting vector modulus in the vicinity of the focus were compared by numerical simulation. It is shown that the degree of their difference increases substantially with decreasing angular zone of annular focusing and with the introduction of spatial-frequency filtering. It is established that the dimensions of the axial zone of beam focusing determined for their central lobes in the first approximation do not depend on the choice of energy characteristics used for their measurements.     

Nano-slit probes for near-field optical microscopy fabricated by focused ion beams

The near-field probes described in this paper are based on metallized non-contact atomic force microscope cantilevers made of silicon. For application in high-resolution near-field optical/infrared microscopy, we use aperture probes with the aperture being fabricated by focused ion beams. This technique allows us to create apertures of sub-wavelength dimensions with different geometries. In this paper we present the use of slit-shaped apertures which show a polarization-dependent transmission efficiency and a lateral resolution of < 100 nm at a wavelength of 1064 nm. As a test sample to characterize the near-field probes we investigated gold/palladium structures, deposited on an ultrathin chromium sublayer on a silicon wafer, in constant-height mode.     

Nano-slit probes for near-field optical microscopy fabricated by focused ion beams

The near-field probes described in this paper are based on metallized non-contact atomic force microscope cantilevers made of silicon. For application in high-resolution near-field optical/infrared microscopy, we use aperture probes with the aperture being fabricated by focused ion beams. This technique allows us to create apertures of sub-wavelength dimensions with different geometries. In this paper we present the use of slit-shaped apertures which show a polarization-dependent transmission efficiency and a lateral resolution of < 100 nm at a wavelength of 1064 nm. As a test sample to characterize the near-field probes we investigated gold/palladium structures, deposited on an ultrathin chromium sublayer on a silicon wafer, in constant-height mode.     

Expanded beam deflection method for simultaneous measurement of displacement and vibrations of multiple microcantilevers

Here we present an extension of optical beam deflection (OBD) method for measuring displacement and vibrations of an array of microcantilevers. Instead of focusing on the cantilever, the optical beam is either focused above or below the cantilever array, or focused only in the axis parallel to the cantilevers length, allowing a wide optical line to span multiple cantilevers in the array. Each cantilever reflects a part of the incident beam, which is then directed onto a photodiode array detector in a manner allowing distinguishing between individual beams. Each part of reflected beam behaves like a single beam of roughly the same divergence angle in the bending sensing axis as the incident beam. Since sensitivity of the OBD method depends on the divergence angle of deflected beam, high sensitivity is preserved in proposed expanded beam deflection (EBD) method. At the detector, each spot's position is measured at the same time, without time multiplexing of light sources. This provides real simultaneous readout of entire array, unavailable in most of competitive methods, and thus increases time resolution of the measurement. Expanded beam can also span another line of cantilevers allowing monitoring of specially designed two-dimensional arrays. In this paper, we present first results of application of EBD method to cantilever sensors. We show how thermal noise resolution can be easily achieved and combined with thermal noise based resonance frequency measurement.     

Nanometer edge profile measurement of diamond cutting tools by atomic force microscope with optical alignment sensor

This paper describes an atomic force microscope (AFM) based instrument for nanometer edge profile measurements of diamond cutting tools. The instrument is combined with an AFM unit and an optical sensor for alignment of the AFM probe tip with the top of the diamond cutting tool edge in the submicrometer range. In the optical sensor, a laser beam from a laser diode is focused to generate a small beam spot with a diameter of approximately 10 μm at the beam waist, and then received by a photodiode. The tool edge top and the AFM probe tip are brought to the center of the beam waist, respectively, through monitoring the variation of the photodiode output. To reduce the influence of the electronic noise on the photodiode output so that the positioning resolution can be improved, a modulation technique is employed that modulates the photodiode output to an AC signal by driving the laser diode with a sinusoidal current. Alignment experiments and edge profile measurements are carried out.     

分散红54掺杂的PMMA聚合物薄膜全光极化的研究

为了扩展全光极化的材料范围 ,制备了以分散红 5 4为客体的 PMMA掺杂型有机聚合物薄膜样品 ,对之进行了全光极化特性的研究 ,极化使薄膜产生二阶非线性 ,种子光的强度越大 ,其二阶非线性极化率达到饱和值越快 ;种子光的位相差、相对强度比、光场强度比等因素影响薄膜的二阶非线性的优劣     

Fabrication of a versatile substrate for finding samples on the nanometer scale

With increasing interest in nanometer scale studies, a common research issue is the need to use different analytical systems with a universal substrate to relocate objects on the nanometer scale. Our paper addresses this need. Using the delicate milling capability of a focused ion beam (FIB) system, a region of interest (ROI) on a sample is labelled via a milled reference grid. FIB technology allows for milling and deposition of material at the sub 20-nm level, in a similar user environment as a standard scanning electron microscope (SEM). Presently commercially available transmission electron microscope (TEM) grids have spacings on the order 100 μm on average; this technique can extend this dimension down to the submicrometre level. With a grid on the order of a few micrometres optical, FIBs, TEMs, scanning electron microscopes (SEMs), and atomic force microscopes (AFM) are able to image the ROI, without special chemical processes or conductive coatings required. To demonstrate, Au nanoparticles of ∼ 25 nm in size were placed on a commercial Formvar^®- and carbon-coated TEM grid and later milled with a grid pattern. Demonstration of this technique is also extended to bulk glass substrates for the purpose of sample location. This process is explained and demonstrated using all of the aforementioned analytical techniques.     

High-Resolution Lithography with Near-Field Optical Microscopy

Scanning near-field optical microscopy (SNOM) is used for lithography to avoid the resolution limiting diffraction of conventional optical methods. We have expanded a commercial SNOM for writing even complex structures on the nanometer scale. Scanning near-field optical lithography (SNOL) has been applied to conventional resists to explore its potential and the possible combination with conventional optical lithography (mix and match technique).