Showing papers on "Zone plate published in 1998"

Imaging of magnetic domains by transmission x-ray microscopy

Abstract: The combination of the high-resolution transmission x-ray microscope (TXM) based on the zone plate technique with the x-ray magnetic circular dichroism (X-MCD) providing a huge magnetic contrast is a new technique to image magnetic domain structures. It is inherently element specific and contains information on the local spin and orbital moments of the absorbing species that can be obtained by applying magneto-optical sum rules. A lateral spatial resolution depending on the quality of the zone plates down to 30 nm can be achieved. We report on first results at the Fe edges of Fe both in amorphous and in multilayered Gd-Fe systems. With a TXM set-up at BESSY I adapted to record magnetic images in varying magnetic fields the evolution of magnetic domains within a complete hysteresis loop and magnetic aftereffects have been studied.

Resolution determination in X-ray microscopy: an analysis of the effects of partial coherence and illumination spectrum

Abstract: Determining the resolution of a zone plate X-ray microscope is a complicated issue, depending on many factors in addition to the quality of the optic. These include the degree of coherence of the illumination, the illumination spectrum, and the nature of the resolution test object. In this paper, we examine closely how the degree of coherence of the illumination affects the resolution as measured with three typical test patterns. In addition, we determine the extent to which the illumination spectrum affects the resolution. We compare X-ray microscope test images to numerical simulations as a function of coherence and illumination spectrum. We are able to conclude that in these experiments, the resolution of the X-ray microscope is 41 nm, or 40% discrepancy is due to aberrations in the objective zone plate lens.

Binary-phase zone-plate arrays based on hybrid solgel glass.

Abstract: An organically modified silane zirconate-based solgel material is used for the fabrication of binary-phase zone-plate arrays. The synthesized hybrid solgel material has a negative tone under UV exposure and can be patterned by a UV-lithography process. The transmittance of the material is nearly 100%, and the refractive index is 1.52. Two different diffractive lens arrays with focal lengths of 5 and 42 cm have been fabricated. The average roughness of the zone surface is less than 20 nm. The diffraction efficiencies of the lens arrays are measured as a function of modulation depth and exposure dose. A diffraction efficiency of 30% is achieved.

Micromachined ultrasonic capacitance transducers for immersion applications

Abstract: Investigations into the characteristics of water-coupled ultrasonic capacitance transducers have been undertaken for a range of transducer configurations. The radiated fields have been scanned in water using a miniature hydrophone detector, and the results compared to theory based on a plane piston approach. Micromachined backplates in conjunction with thin Mylar and mica membranes have been investigated, together with aperture modifications such as an annulus and Fresnel zone plate. The measured results agree well with theory, thus demonstrating that wideband predictable performance (>8 MHz) is obtainable with such transducers. Additionally, pulse-echo C-scans of a Plexiglas plate containing an artificial defect have been undertaken with the capacitance transducer, in order to demonstrate that the capacitance transducer has sufficient sensitivity to allow routine nondestructive testing within immersion applications.

Diffraction type filter having an aberration correction function and wave length selectivity

Abstract: A zone plate having an aberration correcting function in a wavelength selecting manner and a diffraction grating substantially having a light shielding function in a wavelength selecting manner are formed, respectively, in a center region and a marginal region of a filter, whereby only a predetermined wavelength of light is converged or diverged by the zone plate and is diffracted sideways by the diffraction grating, whereby the luminous flux diameter of the irradiation light is changed while the aberration caused by a convergent lens is favorably corrected. The diffraction type filter 8A is constituted by a first region 11 comprising a central circular portion and a second region 12 comprising a marginal portion thereof. The first region 11 is provided with a zone plate 11A (diffraction grating formed like concentric circles) having such a wavelength selectivity that light at a wavelength of 635 nm is transmitted therethrough as it is and that light at a wavelength of 780 nm is converged thereby. The second region 12 is provided with a diffraction grating 12A having such a wavelength selectivity that light at a wavelength of 635 nm is transmitted therethrough as it is and that a major part of light at a wavelength of 780 nm is diffracted sideways so as to be substantially blocked out.

Zone-plate-array lithography in the deep ultraviolet

Abstract: We describe initial steps we have taken in the development of zone-plate-array lithography (ZPAL), a proposed new paradigm for sub-100 nm lithography. The optimal implementation of ZPAL would employ an undulator emitting soft x rays of 4.5 nm wavelength. However, we have opted to concentrate initially on the major uncertainties associated with ZPAL: (1) fabrication of a large array of zone plates with a center-to-center spacing accuracy finer than the minimum zone width, (2) multiplexing of input beams to the individual zone plates, and (3) coordination of that multiplexing with precision motion of a substrate stage. We fabricated arrays of pure-phase zone plates suitable for the 193 nm output of an ArF laser, and conducted exposure tests using a modified Michelson configuration for focusing the zone plate array on the substrate. We also show the first example of simplistic writing. We show that the micromirror array manufactured by Texas Instruments, for use in projection displays, has dimensions and switching characteristics close to those needed for an ultimate ZPAL system.

Influence of roughness and interdiffusion in zone plate structures on the diffraction efficiency described by coupled wave theory

Abstract: Diffractive transmission x-ray optics, e.g., zone plates and gratings, are well suited for x-ray microscopy and spectroscopy. X-ray optics for use at short wavelengths require high zone aspect ratios which can be obtained by alternately depositing two materials with different x-ray scattering properties on a microwire. The roughness and the diffusion inherent to this process influence the diffraction efficiency of these optics. Using coupled wave theory, it is shown that roughness and interdiffusion increase the structure height required for optimal diffraction efficiency compared to ideally smooth structure profiles. In addition, the maximum obtainable diffraction efficiency decreases with increasing root-mean-square roughness and interdiffusion.

Imaging of laser produced plasma at 1.43 keV using Fresnel zone plate and Bragg–Fresnel lens

Abstract: X-ray imaging of plasmas with a resolution on the order of 1 μm could not be achieved with pinholes because the light flux on the detector would be too low. We tested two different types of diffractive lenses derived from the circular grating based on the Fresnel zones. Compared to pinholes, they can have an equivalent diameter of about 100 μm with a resolution of about 1 μm. The two kinds of devices tested were: (1) a transmission phase Fresnel zone lens (PFZL) associated with a multilayer mirror; (2) a reflective Bragg–Fresnel lens (BFL) which combines a multilayer mirror and the grating. The PFZL works at normal incidence by transmission; an additional mirror is used to reflect only a small bandwidth within the spectrum; the angle of reflection of the multilayer of the imaging beam on the mirror is set as to adjust the center of the useful bandwidth. The BFL works at fixed grazing incidence and we only use an off-axis part of the BFL in order to avoid the illumination of the detector by zeroth order di...

X-ray brilliance measurements of a subpicosecond laser plasma using an elliptical off-axis reflection zone plate

Abstract: An absolutely calibrated spectrograph based on a new single x-ray optical element, namely, an elliptical off-axis reflection zone plate, has been used for brilliance measurements of a laser-produced plasma of solid carbon and boron nitride. The spectral range investigated, λ≈2.1–4.3 nm, covers the emission from excited H- and He-like carbon states to the ground state. The plasma was generated by a subpicosecond high-intensity KrF*-laser pulse at an intensity of 2×1016 W/cm2. Under these conditions more than 1011 photons/sr per pulse were emitted in the strongest lines, demonstrating that this plasma can serve as an intense x-ray source. The measured spectra were in good agreement with a simulation that used the radiation program ration for an electron density of ne=4×1022 cm3 and an electron temperature of Te=90 eV. Measurements of spectral changes at different angles of incidence of the laser beam confirmed theoretical predictions for line intensities.

Recent developments in Fresnel zone plate antennas at microwave/millimeter wave

Abstract: The Fresnel zone plate antenna is an example of an optical analogy that has beentransferred to microwave/millimeter wavelength use. The latter case has seen extensive researchand application, and in the past dozen years more than seventy relevant papers have beenpublished on a worldwide basis. These studies have dealt with either lens or reflector designs,and have quantified many parameters, such as gain antenna patterns, efficiency, bandwidth, andstructural options. The most recent designs have dealt with high efficiency or dual bandconfigurations. This report will summarize the many advances ofthe past few years, and willprovide some parametric design tradeoffs.Keywords: Microwave antennas, mil1imeterwave antennas, zoned lenses, low-cost antennas. 1. II'TRODUCTION At microwave and millimeter wavelengths, Fresnel zone plate (FZP) antennas are well-known for their advantages of simplicity ofdesign and construction, low loss (due to reducedthickness), low weight, planar construction, and low cost'. In the last dozen years scores ofpapers have been published describing FZP characteristics, including such parameters asbandwidth, focal behavior, gain, far-field patterns, efficiency, aberrations, off-axis performance,axial intensity dependence, multiple-frequency band performance, and design information1'2.The phase-correcting FZP antenna is a stepped planar lens usually made from low-loss materialssuch as polystyrene, polyethylene, polycarbonate, ceramics or semiconductors. Figure 1 (fromReference 6, Figure 2) illustrates the comparison between a standard lens (spherical orhyperboloidal) and a half-wave FZP, each made from polystyrene and each having a focal lengthand diameter of2O cm. Path length adjustment (i.e., phase correction) is accomplished by cuttingdifferent depths (grooves) in the dielectric plate or by using two or more dielectrics havingdifferent dielectric constants6. The latter case is illustrated in Figure 2 (from Reference 1, Figure

Design and performance of the 2-ID-B scanning x-ray microscope.

Abstract: We have constructed a high resolution scanning x-ray microscope at the 2-ID-B beamline at the Advanced Photon Source for 1-4 keV x-ray imaging and microspectroscopy experiments. The microscope uses a Fresnel zone plate to focus coherent x-ray undulator radiation to a 150 nm focal spot on a sample. The spectral flux in the focus is 10{sup 8} ph/s/0.1% BW. X-ray photons transmitted by the sample are detected by an avalanche photodiode as the sample is scanned to form an absorption image. The sample stage has both coarse and fine translation axes for raster scanning and a rotation axis for microtomography experiments. The incident x-ray beam energy can also be scanned via the 2-ID-B monochromator while the sample is kept in focus to record spatially resolved absorption spectra. We have measured the performance of the instrument with various test objects. The microscope hardware, software, and performance are discussed in this paper.

X-ray telescope for small satellites

Abstract: The study of high energy, transient astrophysical phenomena requires new instrumentation capable of simultaneously performing high spatial, temporal and spectral observations. Currently, there are no elements such as lenses or mirrors capable of reflecting or refracting X- and gamma-rays. Shadow-casting techniques must be employed to image such sources. These techniques rely on the total absorption of X- and gamma-rays to indirectly give images of the sources. We describe here a design for an x-ray telescope based on dual Fresnel Zone Plate (FZP) coders suitable for small satellites. Most shadow-casters requires an image plane detector with a spatial resolution comparable to the smallest features cut into the coder for the best angular resolution. The image plane detector for a telescope based on dual FZPs does not have such a requirement because the coders measure almost the exact spatial Fourier transform of the source distribution. We present here the results of laboratory tests and simulations that demonstrate the feasibility of constructing such a telescope and its ability to produce images of x-ray sources.

High-efficiency high-gain Fresnel zone plate antennas

Abstract: Factors that affect the efficiency of a phase-correcting Fresnel zone plate (FZP) lens antenna are analyzed. These include attenuation, diffraction, and reflection losses. The FZP efficiency is compared to that for a standard lens, and the FZP is shown to be better at millimeter wavelengths, where attenuation is an important factor.

Surface relief zone plates fabricated with photographic emulsions

Abstract: The use of photographic emulsions as a photoresist medium for fabricating relief blazed zone plates is described. Lithographic methods with masks with 256 gray levels were used in the fabrication process. An example of a zone plate working in the reflection mode at 45° and having 82% diffraction efficiency is shown.

Fabrication of intermediate mask for deep x-ray lithography

Abstract: This paper presents the fabrication of intermediate x-ray mask for deep x-ray lithography In order to have working mask with absorbers thickness larger than 10 μm, the intermediate mask should have absorbers of 07 μm in thickness To demonstrate intermediate mask fabrication, x-ray zone plates are fabricated on the 12 μm low-stress silicon-rich silicon nitride (SiNx) membrane with the tri-layer Chromium-Tungsten-Chromium (Cr–W–Cr) as the x-ray absorbers The chromium layers both 200 angstroms are used as adhesion and for stress relief The SiNx film is deposited with low pressure chemical vapor deposition (LPCVD) and the free standing membrane are formed by KOH silicon backside etching With the e-beam lithography and reactive ion etching, width of 08 μm of outmost zone of the x-ray zone plates has been achieved on the membrane The scanning electron microscopy (SEM) images of the x-ray zone plates and pictures of intermediate masks are demonstrated

Phase zone plates for hard x-ray microscopy

Abstract: Phase zone plates are commonly used in x-ray microscopy techniques when high spatial resolution and high photon flux in the focal spot are desired. Extending the fabrication techniques of phase zone plates for use in the soft x-ray region to higher photon energies becomes difficult due to the high aspect ratios of the zone structures which have to be created. As an alternative, the sputtered sliced zone plate method has been applied. In this technology, a thin microwire is deposited alternately with two different materials. Zone plates are generated from the rod by slicing it perpendicular to its axis and thinning the slices down the required zone plate thickness. Theoretical investigations on the demands on generating these zone plates as well as the generation process are discussed. Recent measurements will be presented.

Modern VUV and x-ray micro-optics: LIGA-fabricated and micromachined devices

Abstract: Deep x-ray lithography, together with high quality electrogrowth (LIGA) is known for its capacity in fabricating extreme high aspect ratio structures of very good sidewall roughness and perpendicularity. Since LIGA-resists are plastics, and elastically deformable, we describe the physics and fabrication of Orthogonal Reflection Optics (ORO), LIGA- based multimirror lenses. Such optics operate by reflections from precisely inclined sidewalls. Diffraction calculations show excellent behavior in comparison even to Fresnel zone plates. OROs produce piecewise linear approximations of ideal lenses and can perform accordingly. Unlike classical lenses, OROs may work well in the VUV and soft x-ray region, and even for hard x-rays or function as particle-optics. OROs can be designed intrinsically achromatic. OROs are lightweight, quite planar and a large number of material choice exists for adjusting lens behavior to desired functions, e.g. high melting point metals (Pt, Os) for very heat resistant lenses operating above 2000 K. A classification of an entire ORO family, together with other modern concepts concerning x-ray micro transmission lenses by micromachining is included. First fabrications of 2D and 1D planar ORO-Fresnel lenses by LIGA are described.

High-resolution phase zone plates for water window wavelengths

Abstract: High-resolution x-ray microscopy has applications in the fields of biology, colloid physics, and solid state physics. For each of these applications it is essential that the micro zone plates used as objectives in the x-ray microscope combine high resolution with optimal diffraction efficiency, so as to minimize exposure time and the x-ray dose absorbed by the specimen. The outermost zone width constitutes an important property of the zone plate, since the first-order spatial resolution scales linearly with this parameter. The other fundamental property of a micro zone plate is its diffraction efficiency, which should be both high and uniform. The combination of small outermost zones and the zone height required for optimal diffraction efficiency leads to high aspect ratios of the nanostructures. We report here the technique to manufacture these micro zone plates using microscopic glavanoforms and electrodeposition. Copolymer galvanoforms for nickel micro zone plates were irradiated with high doses of x-ray radiation to increase the degree of cross-linking of the copolymer network in this way, exact pattern replication in the galvanoform was obtained for zone aspect ratios of up to 8:1. Using these galvanoforms, nickel micro zone plates were produced for the soft x-ray wavelength 2.4 nm, with smallest zone widths of 30 nm and 40 nm, achieving first-order diffraction efficiencies of up to 15 percent and 20 percent, respectively.

Synchrotron Radiation Hard X-Ray Microprobe by Multilayer Fresnel Zone Plate

Abstract: A hard X-ray microbeam with submicrometer spot size from synchrotron radiation (SR) sources is expected to add a new dimension to various X-ray analysis methods. A Fresnel zone plate (FZP) is one of the promising focusing elements for X-rays. In order to develop high performance multilayer FZP for use in the hard X-ray region, Cu/Al concentric multilayers were fabricated by use of a DC sputtering deposition process. Lower Ar gas pressure or higher rotating speed of a wire substrate has been effective in forming smoother multilayer interfaces. From a focusing test of the Cu/Al FZP (100-zones) by the SR (λ= 0.154nm), microbeams of 1.5 μm φ and 0.8 μm φ have been achieved for the first- and third-order focal beams, respectively.

High Numerical-Aperture X-Ray Condensers for Transmission X-Ray Microscopes

Abstract: In the near future transmission X-ray microscopes (TXM) will be installed at undulator X-ray sources, which generate highly collimated X-ray beams. To match a TXM to such a source X-ray condenser-monochromators of smaller light collecting area and increased numerical aperture (NA) are required. This can be achieved with the concept of dynamical aperture synthesis. Herein an off-axis zone plate with comparatively “coarse” zones is used, which can be processed with high diffraction efficiency with standard ebeam lithography methods. The numerical aperture of any existing X-ray micro objective can be matched for dark and bright field imaging. A monochromaticity of several thousand is possible and the homogeneity of the intensity distribution in the object field is enhanced compared to a zone plate linear monochromator used in TXMs at the moment.

Fluorescent microscope of x-ray excitation type

Abstract: PROBLEM TO BE SOLVED: To make it possible to detect a specific chemical group or element by exciting the photon energy of a specific value or lower with X rays which are made monochrome. SOLUTION: X rays which are generated by making the photon energy radiated from a synchrotron 1 monochrome at about 2000eV or lower are dispersed by a diffraction grating 2 and are condensed on the first pinhole 4 by an oblique-incidence condensing lens 3. A point image on the first pinhole 4 is reduced and formed at a point in an observed sample 6 by a fresnel zone plate 5, and an X-ray microbeam of a few dozens nanometers in size is made. Consequently, the fluorescence emitted from the observed sample 6 is condensed on the second pinhole 8 by a visible and ultraviolet light lens 7 in a visible or ultraviolet range and is gathered on a photomultiplier 9. This makes it possible to detect a specific chemical group and a trace of it and improve the contrast of an obtained image.

Bend magnet beamline for scanning transmission x-ray microscopy at the Advanced Light Source

Abstract: A bend magnet at the advanced light source is sufficiently bright to illuminate a scanning transmission x-ray microscope, with a zone plate lens to focus the soft x-ray beam at the diffraction limit. The beam line must be carefully optimized for this one purpose of high count-rates, of the order of 1MHz, are to be achieved in the microscope. Such a design is described. The nominal resolving power is 2000 from 150eV to 600eV using a single spherical diffraction grating. Twice the resolving power is available at reduced flux, and the intensity can be traded independently against the spatial and spectral resolution.

Diffraction characteristics of the ring zone plate as a representative of curvilinear zone plates

Abstract: It is shown that curvilinear zone plates can be constructed as phase representatives of plane curvilinear light sources. The ring zone plate is one representative of this type of diffracting optical element. At the same time, it is an optical device which can be used as a lens substitute for ring lenses, especially in the UV region. The diffracted wave amplitude and the intensity distribution for both binary, positive and negative, computer-generated ring zone plates, are determined by the use of the Fresnel-Kirchoff approximation. It is found that the ring zone plate exhibits manifold real and virtual focal rings.

Zone Plates for a Scanning Transmission X-Ray Microscope

Abstract: We describe the use of a commercial e-beam lithography machine for zone plate fabrication. We have modified the software of a JEOL JBX-6000FS, so as to draw high quality circular figures with a current of up to 500 pA within a 7 nm beam spot. Zone plates fabricated in germanium show good efficiency and resolution for scanning transmission x-ray microscopy applications. Zone plates with diameters larger than a writing field were successfully written by stitching together multiple fields.

Ti/Al multilayer zone plate and Bragg-Fresnel lens.

Abstract: By using a helicon plasma sputtering technique, a one-dimensional Ti/Al multilayer zone plate with an outermost layer width of 76 nm has been successfully fabricated. A Bragg–Fresnel lens has been made by combining this zone plate with a Ge(422) crystal. Comparison of the Ti/Al multilayer zone plate with the Ag/Al zone plate is discussed in terms of focusing efficiency.

New types of Fresnel zone plate lens with lower backward radiation

Abstract: Owing to its low cost, light weight, and easy fabrication, the Fresnel zone plate (FZP) antenna is becoming an important candidate for such applications as DBS reception and mobile communication. Compared with the FZP reflector, the FZP lens has no feed blockage, so it is more attractive to study. The printed FZP lens, in which the concentric zones are alternatively transparent and opaque, is discussed in this paper. However, the single-layer FZP has a rather low efficiency, for about half of the incident energy is reflected backward, so the double-layer FZP lens had been proposed to enhance the aperture efficiency. By using an improved full-wave analysis the double-layer FZP lens is studied.

Holographic projection screen having a rear-facing fresnel lens

Abstract: A screen for a projection-type video display apparatus. A linear-type Fresnel lens has a lens pattern on a first side for receiving light energy from a light source. A second side of the Fresnel lens is opposite the first side. The light energy exits the Fresnel lens from the second side. A hologram is affixed to the second side of the Fresnel lens for managing the dispersion of the light energy exiting from the second side of the Fresnel lens. The hologram is affixed to the Fresnel lens by any of various lamination processes.