Holographic interference microscope for laboratory studies

A digital holographic interference microscope is designed that allows real-time 3D imaging of phase microobjects and measurement of their morphological parameters. The instrument may find application in medical institutions and research laboratories.     

Transmission-type high-resolution laser scanning microscope

Optical Review - To visualize the microscopic internal structure of cells, some conventional methods exist in the literature, such as irradiating fluorescent substances with light that maintains...     

Dual-axis confocal microscope for high-resolution in vivo imaging

We describe a novel confocal microscope that uses separate low-numerical-aperture objectives with the illumination and collection axes crossed at angle theta from the midline. This architecture collects images in scattering media with high transverse and axial resolution, long working distance, large field of view, and reduced noise from scattered light. We measured transverse and axial (FWHM) resolution of 1.3 and 2.1 microm, respectively, in free space, and confirm subcellular resolution in excised esophageal mucosa. The optics may be scaled to millimeter dimensions and fiber coupled for collection of high-resolution images in vivo.     

Basic characteristics of interference image obtained using spatially phase-modulated mirror array

Single-shot full-field optical coherence tomography (OCT) using spatially phase-modulated reference light has been proposed to achieve a higher sensitivity.16) The reference light can be generated by a spatially phase-modulated mirror array (SPMA). The basic characteristics of an interference image using SPMA have been demonstrated using a superluminescent diode (SLD) with a center wavelength of 840 nm as a popular low-coherence light source. SPMA consisted of a small mirror of 10 × 10 mm² and had a full area of 5 × 5mm². The magnifications in the reference arm were 3, 2, and 1. The corresponding magnifications in the signal arm were 18.1, 12.2, and 5.2. The ratios of the interference area to the full CCD area were 0.68, 0.32, and 0.13. Visibilities and ratios for calculations were measured at 0.38 (54%), 0.19 (28%), and 0.062 (8.2%). The periodical background noise was high owing to interferences with scattered lights from SPMA. From the spectra of signal intensity profiles in the subtracted image between two interference images, it was confirmed that the optical phase in the reference light was spatially and periodically modulated by SPMA.     

A novel high-resolution interference spectrometer

A novel precision wavemeter is presented with a resolution of better than 0·01 nm. A Sagnac interferometer with two diffraction gratings forms the basis of the instrument. Using spatial heterodyning techniques and a CCD camera/frame grabber data acquisition system allows fast computer control and power spectrum analysis. The mode structure and mode hopping characteristics of a typical laser diode were examined as a function of diode injection current.     

A high-resolution spatial heterodyning interference spectrometer

A novel spectrometer which has a resolution of 0.013 nm with high throughput is described. The system uses a Michelson interferometer in which the mirrors have been replaced with Littrow-mounted diffraction gratings. First-order diffracted beams returning from the gratings interfere at the interferometer output to produce a spatial interferogram which is heterodyned about an optical frequency determined by the setting angles of the gratings. The heterodyning process leads to increased resolution, but limits the free-spectral range of the instrument to, in our case, about 3 nm. This is sufficient for characterizing narrow-band sources such as laser diodes. We present the theory of operation of the instrument and some sample spectra obtained from a sodium vapor lamp, a HeNe discharge, and a 670 nm diode laser.     

Force-feedback high-speed atomic force microscope for studying large biological systems

We designed and developed a high-speed atomic force microscope (HSAFM) utilizing a force-feedback scheme for imaging large biological samples. The system collects three simultaneous images: a deflection image, a topographic image, and a force image. We demonstrated that this force-feedback HSAFM is capable of acquiring large topographic images of Escherichia coli biofilms at approximately one frame per second in air. We discuss how the self-actuating cantilever and the piezo tube follow those larger biological topographic features during the HSAFM imaging process.     

A compact high-speed mechanical sample shuttle for field-dependent high-resolution solution NMR

Analysis of NMR relaxation data has provided significant insight on molecular dynamic, leading to a more comprehensive understanding of macromolecular functions. However, traditional methodology allows relaxation measurements performed only at a few fixed high fields, thus severely restricting their potential for extracting more complete dynamic information. Here we report the design and performance of a compact high-speed servo-mechanical shuttle assembly adapted to a commercial 600 MHz high-field superconducting magnet. The assembly is capable of shuttling the sample in a regular NMR tube from the center of the magnet to the top (fringe field ～0.01 T) in 100 ms with no loss of sensitivity other than that due to intrinsic relaxation. The shuttle device can be installed by a single experienced user in 30 min. Excellent 2D-(15)N-HSQC spectra of (u-(13)C, (15)N)-ubiquitin with relaxation at low fields (3.77 T) and detection at 14.1T were obtained to illustrate its utility in R(1) measurements of macromolecules at low fields. Field-dependent (13)C-R(1) data of (3,3,3-d)-alanine at various field strengths were determined and analyzed to assess CSA and (1)H-(13)C dipolar contributions to the carboxyl (13)C-R(1).     

Development of a scanning Hall probe microscope for simultaneous magnetic and topographic imaging

A scanning Hall probe microscope that is capable of observing both topographic and magnetic images simultaneously has been developed by constructing a conducting needle, used for the scanning tunneling microscope (STM) measurements, adjacent to the Hall junction of 0.6 μm square. The needle also enables the Hall probe to approach the sample without contact and to scan just above it with close proximity. Morphologies and local magnetic distributions on the surfaces of magnetic recording media, observed by our microscope, indicates that lateral spatial resolution is better than 1 μm for both STM and magnetic measurements.     

Interpulse interference of electron emission from an atom irradiated by sinusoidally phase-modulated pulse

We theoretically investigate the photoelectron emission from an atom irradiated by an amplitude modulated sinusoidally phase-modulated pulse through solving the time-dependent Schr¨odinger equation in the momentum space. By controlling the phase amplitude of the pulse in the frequency domain, it can be found that the photoelectron spectra appear as explicit interference phenomena, which originated from the interference between the directly ionized electron and the ionization of the pre-excited atom from different subpulses.     

Nanostructure identification using interference microscope with database

Interference microscopy with complex-amplitude pattern matching between an observed image and images stored in a database can observe nanostructures beyond the diffraction limit of light. The fundamental performance was investigated from size measurement of a single rectangular convex element with a height and width less than 100 nm under illumination light with a wavelength of 400 nm, using an objective lens with a numerical aperture of 0.85. A 50 nm rectangular convex element was reconstructed with an identification error rate of less than 1% and a root-mean square error lower than 1 nm in the presence of random noise. The element height could be detected with a lower error than its width when the element size was larger than ~?50 nm. However, this tendency reversed when the size was smaller than ~?50 nm, that is, the detection of the width had a slightly lower error than that of the height. In addition to these findings, position detection showed a small dependency on the element size when the position was in the laser beam.     

A scanning superconducting quantum interference device microscope for room temperature samples

We have constructed a scanning low-T_c superconducting quantum interference device (SQUID) microscope, in which the SQUID is mounted on the lower end of a copper rod and cooled to liquid helium temperature. There is a 65μm thick sapphire window under the SQUID. The sample at room temperature underneath the window can be scanned to produce magnetic images. The microscope has a spatial resolution of 100－150μm and a magnetic field sensitivity of 3－60pT/$\sqrt{Hz}$ in a magnetically unshielded environment. We have used this scanning SQUID microscope to measure various room temperature samples.     

Compression dynamics for phase-modulated few-cycle pulses

A theory of compression of short optical pulses with quadratic phase modulation in a dispersive medium has been developed. The results of numerical simulation of the equation for the light wave field are reported. The conditions are found at which a pulse is compressed to one oscillation period. The optimal phase modulation index providing the maximum pulse compression is estimated.     

Full-field heterodyne interference microscope with spatially incoherent illumination

A heterodyne interference microscope arrangement for full-field imaging is described. The reference and object beams are formed with highly correlated, time-varying laser speckle patterns. The speckle illumination confers a confocal transfer function to the system, and by temporal averaging, the coherence noise that often degrades coherent full-field microscope images is suppressed. The microscope described is similar to a Linnik-type microscope and allows the use of high-numerical-aperture objective lenses, but the temporal coherence of the illumination permits the use of a low-power achromatic doublet in the reference arm. The use of a doublet simplifies alignment of the microscope and can reduce the cost. Preliminary results are presented that demonstrate full-field surface height precision of 1 nm rms.     

用干涉显微镜测量薄膜厚度的改进与分析

将干涉显微镜的应用推广到透明薄膜厚度的测量,扩展了干涉显微镜的测量范围和应用领域.基于菲涅耳公式,分析了透明薄膜界面的反射.根据白光干涉原理,利用圆形样品台的定量移动,实现了薄膜厚度的测量.     

A four-channel multilayer KB microscope for high-resolution 8-keV X-ray imaging in laser-plasma diagnostics

A four-channel multilayer Kirkpatrick-Baez(KB) microscope is developed for the 8-keV X-ray imaging of experiments on laser inertial confinement fusion(ICF).A periodic multilayer that works at 8 keV and with a grazing incidence angle of 1.0° is coated on reflective surfaces to achieve a spatial resolution higher than 5μm and an effective solid angle higher than ～10-7sr.A precise assembly is realized by a conical reference cone to couple with an X-ray framing camera.This study provides detailed information on an optical and multilayer design,assembly method,and experimental results with a Cu X-ray tube.The instrument provides a high-resolution and high-throughput X-ray image for backlit or self-emission imaging of laser plasma at Cu Kαline radiation in Shenguang series laser facilities.     

Subsurface defect detection in ceramics by high-speed high-resolution optical coherent tomography

We use optical coherence tomography with a new configuration to determine the size and location of subsurface defects in solid ceramic and composite ceramic materials. Cross-sectional subsurface regions either parallel or perpendicular to the surface were examined. We present experimental results showing that the size and distribution of small subsurface defects can be determined with depth and lateral resolutions of 10 and 4 microm, respectively.     

Geometrical cross-sectional imaging by a heterodyne wavelength-scanning interference confocal microscope

We developed a heterodyne interference confocal microscope, using wavelength modulation of a laser diode to realize quick separate measurement of the refractive indices and geometrical thicknesses of multiple layers. This microscope requires only a single axial movement of the specimen. We can display the geometrical cross sections of the interfaces and the refractive indices of a three-layered object.     

Solid-gas reactions of complex oxides inside an environmental high-resolution transmission electron microscope

In a gas reaction cell (GRC), installed in a high-resolution transmission electron microscope (HRTEM) (JEOL 4000EX), samples can be manipulated in an ambient atmosphere (p<50mbar). This experimental setup permits not only the observation of solid-gas reactions in situ at close to the atomic level but also the induction of structural modifications under the influence of a plasma, generated by the ionization of gas particles by an intense electron beam. Solid state reactions of non-stoichiometric niobium oxides and niobium tungsten oxides with different gases (O2, H2 and He) have been carried out inside this controlled environment transmission electron microscope (CETEM), and this has led to reaction products with novel structures which are not accessible by conventional solid state synthesis methods.Monoclinic and orthorhombic Nb(12)O(29) crystallize in block structures comprising [3x4] blocks. The oxidation of the monoclinic phase occurs via a three step mechanism: firstly, a lamellar defect of composition Nb(11)O(27) is formed. Empty rectangular channels in this defect provide the diffusion paths in the subsequent oxidation. In the second step, microdomains of the Nb(22)O(54) phase are generated as an intermediate state of the oxidation process. The structure of the final product Nb(10)O(25), which consists of [3x3] blocks and tetrahedral coordinated sites, is isostructural to PNb(9)O(25). Microdomains of this apparently metastable phase appear as a product of the Nb(22)O(54) oxidation. The oxidation reaction of Nb(12)O(29) was found to be a reversible process: the reduction of the oxidation product with H(2) results in the formation of the starting Nb(12)O(29) structure. On the other hand, the block structure of Nb(12)O(29) has been destroyed by a direct treatment of the sample with H(2) while NbO in a cubic rock salt structure is produced.This in situ technique has also been applied to niobium tungsten oxides which constitute the solid solution series Nb(8-n)W9(+n)O47 with 0< or =n< or =4. All of these phases crystallize in the threefold tetragonal tungsten bronze (TTB) superstructure of Nb(8)W(9)O(47) (n=0). In the main reaction, these phases decompose in a gas plasma (O2, H2 or He, p=20mbar) into WO(3-x), which evaporates and solidifies again near the irradiated crystallite, and (Nb,W)(24)O(64), which crystallizes in a 2a superstructure of the TTB type observed here for the first time in the system Nb-W-O. Nb(8)W(9)O(47), Nb(7)W(10)O(47) and Nb(6)W(11)O(47) always react in this way, independent of the applied gas. On the other hand, the treatment of Nb(5)W(12)O(47) (n=3) and Nb(4)W(13)O(47) (n=4) in an oxygen atmosphere often caused a different reaction: these phases have been oxidized and a heavily disordered bronze-type structure has been formed. The oxygen excess in these products is largely accommodated in segregated domains of WO(3).