Laminar Gratings Research Articles

High efficiency multilayer coated laminar gratings with high line density for tender X-ray region

Driven by the demand of high efficiency and high resolution monochromators and spectrometers in the tender X-ray range, high line density multilayer coated laminar gratings (MLLG) were designed, manufactured, and analyzed. Theoretical simulations displayed that a 5000 l/mm MLLG could realize high resolution at 3 keV and 40 times higher diffraction efficiency than the single-layer coated grating. For the first demonstration of the high line density MLLGs, two 3000 l/mm laminar gratings were fabricated and coated by Cr/C multilayers with different periodic thicknesses to achieve high efficiency (HE) and high resolution (HR) performance. For MLLG-HE, a maximum efficiency of 54.5% was achieved at 4.4 keV. For MLLG-HR, relatively high efficiency of 23.1%–38.6% were demonstrated with much stronger asymmetric diffraction in 2–4 keV, which can significantly increase the energy resolution of the system.

Gratings for synchrotron and FEL beamlines: aproject for the manufacture of ultra-precise gratings at Helmholtz Zentrum Berlin.

Blazed gratings are of dedicated interest for the monochromatization of synchrotron radiation when a high photon flux is required, such as, for example, in resonant inelastic X-ray scattering experiments or when the use of laminar gratings is excluded due to too high flux densities and expected damage, for example at free-electron laser beamlines. Their availability became a bottleneck since the decommissioning of the grating manufacture facility at Carl Zeiss in Oberkochen. To resolve this situation a new technological laboratory was established at the Helmholtz Zentrum Berlin, including instrumentation from Carl Zeiss. Besides the upgraded ZEISS equipment, an advanced grating production line has been developed, including a new ultra-precise ruling machine, ion etching technology as well as laser interference lithography. While the old ZEISS ruling machine GTM-6 allows ruling for a grating length up to 170 mm, the new GTM-24 will have the capacity for 600 mm (24 inch) gratings with groove densities between 50 lines mm-1 and 1200 lines mm-1. A new ion etching machine with a scanning radiofrequency excited ion beam (HF) source allows gratings to be etched into substrates of up to 500 mm length. For a final at-wavelength characterization, a new reflectometer at a new Optics beamline at the BESSY-II storage ring is under operation. This paper reports on the status of the grating fabrication, the measured quality of fabricated items by ex situ and insitu metrology, and future development goals.

Design, development and applications of etched multilayers for soft X-ray spectroscopy

An etched multilayer, a 2D structure fabricated by etching a periodic multilayer according to the pattern of a laminar grating, is applied in the soft X-ray range to improve the spectral resolution of wavelength dispersive spectrometers. The present article gathers all the successive stages of the development of such a device optimized to analyze the characteristic emission of light elements: design, structural and optical characterization and applications to X-ray spectroscopy. The evolution of the shape of the C Kα emission band of highly oriented pyrolytic graphite (HOPG), as a function of the angle between the emission direction and the (0 0 0 1) planes, is measured. These results, compared to those with a grating, demonstrate that the achieved spectral resolution enables disentangling σ → 1s and π → 1s transitions within the C K emission band.

Modeling and empirical characterization of the polarization response of off-plane reflection gratings.

Off-plane reflection gratings were previously predicted to have different efficiencies when the incident light is polarized in the transverse-magnetic (TM) versus transverse-electric (TE) orientations with respect to the grating grooves. However, more recent theoretical calculations which rigorously account for finitely conducting, rather than perfectly conducting, grating materials no longer predict significant polarization sensitivity. We present the first empirical results for radially ruled, laminar groove profile gratings in the off-plane mount, which demonstrate no difference in TM versus TE efficiency across our entire 300-1500eV bandpass. These measurements together with the recent theoretical results confirm that grazing incidence off-plane reflection gratings using real, not perfectly conducting, materials are not polarization sensitive.

Near-field holography enhanced with antireflection coatings—an improved method for fabricating diffraction gratings

Near-field holography (NFH), with its virtues of precise critical dimensions and high throughput, has a great potential for the realization of soft x-ray diffraction gratings. We show that NFH with reflections reduced by the integration of antireflective coatings (ARCs) simplifies the NFH process relative to that of setups using refractive index liquids. Based on the proposed NFH with ARCs, gold-coated laminar gratings were fabricated using NFH and subsequent ion beam etching. The efficiency angular spectrum shows that the stray light of the gratings is reduced one level of magnitude by the suppression of interface reflections during NFH.

Metrology, Mirrors and Gratings – Advances and Challenges in Synchrotron Optics

Ultra-precise reflective and diffractive optical elements like blazed diffraction gratings or ultra-precise mirrors of flat, elliptic, parabolic, or other shapes have become key components in today's synchrotron optics. These optical components feature nanometre accuracy on a macroscopic length scale. Beamlines with extreme lengths of 100m to 1km or more (as planned for the European XFEL) will require plane mirrors characterized by a residual slope error of 50nrad rms and a curvature radius of > 1000km on a length of 800mm or even more. Diffraction limited focusing mirrors for hard X-ray application show residual slope deviations of 50nrad rms on a length of 350mm. The current slope limit for focusing mirrors in VUV-application lies at around 0.5μrad rms, one order of magnitude inferior compared to hard X-ray focusing optics, and it can still not be exceeded due to technological restrictions. The requirements for diffraction gratings are even more challenging. In addition to the challenges posed by perfect substrate quality, special attention is needed to guaranty a precise positioning of the grooves along the full aperture length. A positioning accuracy of about 20nm for the carriage system of a ruling engine is mandatory to meet the Marechal tolerance for gratings. For the manufacture of blazed and laminar gratings, we are currently establishing a new technological laboratory at the Helmholtz Zentrum Berlin (HZB), including instrumentation from Carl Zeiss. Besides the present Zeiss technology, we are also developing an advanced technology line, including a new ultra-precise ruling machine, ion etching technology as well as laser holography.

Laminar and blazed type holographic gratings for a versatile soft x-ray spectrograph attached to an electron microscope and their evaluation in the 50–200 eV range

Laminar and blazed type holographic varied-line-spacing spherical gratings for use in a versatile soft x-ray flat-field spectrograph attached to an electron microscope are designed, fabricated, and evaluated. The absolute diffraction efficiencies of laminar (or blazed) master and replica gratings at 86.00° incidence evaluated by synchrotron radiation show over 5% (or 8%) in the 50-200 eV range with the maxima of 22% (or 26%-27%). Also the resolving power evaluated by a laser produced plasma source is in excess of 700 at the energy near the K emission spectrum of lithium (~55 eV) for all gratings. Moreover, the K emission spectrum of metallic Li with high spectral resolution is successfully observed with the spectrograph attached to a transmission electron microscope.

多层膜沉积对光栅衬底槽形影响研究

Diffraction efficiency is critical for EUV multilayer gratings.To realize high diffraction efficiency,appropriate multilayer deposition method should be developed for grating substrates to ensure their groove shapes.The evolvement of groove shapes for laminar gratings during the deposition process was investigated.The results showed that the period number of the coating was a critical factor.To conserve groove shapes,period number should be selected appropriately for ultra shallow laminar gratings with depth of 2～5 nm.In the guideline of this principle,multilayer laminar grating with a diffraction efficiency of 22.1% at 14.65 nm on the-1 order was achieved,which exceeded all other results reported to date.

Investigation on the properties of a laminar grating as a soft x-ray beam splitter

Laminar-type gratings as soft x-ray beam splitters for interferometry are presented. Gold-coated grating beam splitters with 1000 lines/mm are designed for grazing incidence operation at 13.9 nm. They are routinely fabricated using electron beam lithography and ion etching techniques. The laminar grating is measured to have almost equal absolute efficiencies of about 20% in the zeroth and -1st orders, which enables a fringe visibility up to 0.99 in the interferometer. The discrepancy of the grating profiles between the optimized theoretical and the experimental results is analyzed according to the comparison of the optimized simulation results and the measurement realization of the grating efficiencies. By a precise control of the grating profile, the grating efficiency in the -1st order and the fringe visibility could be improved to 25% and 1, respectively.

Design of a high-efficiency grazing incidence monochromator with multilayer-coated laminar gratings for the 1–6 keV region

A grazing incidence objective monochromator consisting of a spherical mirror, a varied-line-spacing plane grating with multilayered coating, a movable plane multilayered mirror, and a fixed exit slit for the 1–6 keV region has been designed. The included angle at the grating was chosen to satisfy the grating equation and extended Bragg condition simultaneously. The aberration was corrected by means of a hybrid design method. A spectral resolving power of ∼600–∼6000 and a throughput of ∼2%–∼40% is expected for the monochromator when used in an undulator beamline.

Dispersive x-ray absorption spectroscopy with gratings above 2 keV

Laminar gratings can be used to perform x-ray absorption measurements dispersively in energy, thereby making an efficient use of the available x-ray intensity. To examine the performance of a laminar grating in diffracting short wavelength x rays, efficiency measurements of a 600l∕mm grating were performed over the photon energy range from 3 to 8 keV. A peak efficiency of 5.8% was observed without surface normal rotation (SNR); with a SNR of 60° a maximum efficiency of 14.1% was measured. The measured grating efficiencies are in good qualitative agreement with values calculated by a code based on the Neviere theory. By considering both the peak efficiency and the diffracted bandwidth, a gain of 97 is obtained for the 600l∕mm grating with a SNR of 60° in comparison with a germanium (111) crystal. Sufficient energy resolution for extended x-ray absorption fine structure experiments can be achieved by a grating at short wavelengths.

Normal-incidence efficiencies of multilayer-coated laminar gratings for the Extreme-Ultraviolet Imaging Spectrometer on the Solar-B mission

The normal-incidence efficiencies of two laminar gratings and the reflectances of two parabolic mirrors with matching multilayer coatings were measured by monochromatic synchrotron radiation and were compared with modeling calculations. These optics were developed for the Extreme-Ultraviolet Imaging Spectrometer to be launched on the Japanese Solar-B mission. Each optic has two sectors coated with Mo/Si multilayers that reflect the 17-21-nm and 25-29-nm wave bands at normal incidence. The measured peak grating efficiencies are in the 8%-12% range and are in good agreement with efficiency calculations that account for the effects of groove profile and the microroughness as determined by atomic force microscopy.

高分解能プラズマ X 線計測の最前線 6.高分解能分光•画像計測用 X 線光学素子の最前線 6.1 軟 X 線ラミナー型不等間隔溝ホログラフィック回折格子

Laminar-type varied-line-spacing gratings have been widely used for soft x-ray monochromator recently because of the features of low stray lights and higher order lights. We have developed an advanced holographic recording and an ion-beam etching methods for the laminar type varied-line spacing gratings. This report describes a short review of the soft x-ray spectrometers using varied-line-spacing gratings, the fabrication process of the laminar-type holographic gratings, and the performance of the flat field spectrographs equipped with the laminar type varied-line spacing gratings comparing with the mechanically ruled replica gratings. It is concluded that, for the sake of the advanced design and fabrication processes and excellent spectroscopic performance, laminar-type holographic gratings will be widely used for soft x-ray spectrometers for various purposes in the near future.

Polarization Performance of a New Spectrometer Based on a Multilayer-Coated Laminar Grating in the 150-190-eV Region

We constructed a polarization spectrometer based on a laminar grating applied with a Mo/B4C multilayer coating. The multilayer-coated grating had been previously evaluated to have high polarizance at around 6.7 nm (184 eV) due to the Brewster reflection. In this study the polarization spectrometer was found to be usable in a range from 150 to 190 eV. Using it, σ and π emission spectra in the B 1s emission from a CrB2 single crystal were separately recorded for the first time in the soft x-ray region. The spectral feature of the emission was reasonably well reproduced by the band calculation.

Efficiency and polarization performance of a multilayer-coated laminar grating in the 6.5-6.9-nm wavelength region.

We applied a Mo/B4C multilayer coating to a laminar holographic grating with 2400 grooves/mm and a 1-m radius of curvature. By use of synchrotron soft x rays the multilayer-coated grating was evaluated to have diffraction efficiencies of 3.1% and 0.017% for s- and p-polarized radiation, respectively, at a 6.7-nm wavelength at a 45.35 degrees grazing angle of incidence in the +1 (inside) grating order. Thus the polarizance was estimated to be 98.9% at least. The zero-order peak was suppressed by the destructive interference caused by the groove profile.

Investigation of the properties of an ion-etched plane laminar holographic grating

We have measured the efficiency over the range 125-225 A of a bare ion-etched plane laminar holographic grating made of fused silica and with 1000 grooves/mm. The measured efficiency of each order oscillates with wavelength because of constructive and destructive interference between radiation diffracted from the lands and the grooves. We measured the grating groove profile with an atomic force microscope, and the resulting groove depth of 434 ? 6 A agrees well with the values determined independently from the oscillatory behavior of the efficiency measurements. Grating efficiency in the +1 order peaked at values of 0.027%, 0.011%, and 0.005% at wavelengths of 191, 157, and 132 A, respectively; and the derived groove efficiencies are 27%, 25%, and 27%. The irregular shape at the land-groove edges dominates the large grating roughness of 23-45-A rms, but even regions far from the edges have a roughness of 10-18-A rms. The average groove profile was used to model the grating efficiency, and the resulting wavelengths predicted for different order maxima and minima agree well with measured wavelengths, although the calculated efficiencies are greater than the measured results by 10-20%.

Integral calculation method of the efficiencies of laminar stratified gratings

We present an integral calculation method of the efficiencies of laminar stratified gratings. By stratified grating, we mean a medium whose optical index varies with the depth. The calculation is applied to the Bragg-Fraunhofer optics recently developed for the X-UV optics. The results of the method are compared to modal or differential methods already implemented for lamellar multilayer amplitude gratings.

Zero-Order-Free, Multilayer-Coated Laminar Grating in the 31 nm Region

A laminar holographic grating was coated with a Mo/Si multilayer and the grating efficiency was measured between 27 and 35 nm for an incidence angle of 10°. The zero order was almost suppressed by the negative interference due to the groove profile. The maximum efficiency of first order was 4.8% at 31 nm. It was also found that the spectral wavelength provided by the grating at 10° incidence ranges from 28 nm to 32 nm.

Transmission light microscopy of structurally colored semithin cartilage sections.

Conversion of osmified tracheal cartilage constituents into an array of laminar interference gratings has been attained by three tandem reactions. Oxidation of semithin, LR white-embedded cartilage sections by acetic anhydride in dimethyl sulfoxide is the first step in the conversion process. Subsequent addition reactions of oxidized cartilage pyranoses and furanoses with thiocarbohydrazide constitutes the second step. Reduction of silver proteinate by thiocarbohydrazones and the concomitant coating of cartilage constituents with silver gratings completes the conversion of cartilage sections into a system of layered interference filters. In transmitted light, all components of converted cartilage display vivid structural colors, which allow detailed microscopic analysis of structurally colored cellular and extracellular cartilage constituents.

Efficiency of a multilayer-coated, ion-etched laminar holographic grating in the 145–160-nm wavelength region

The efficiency of an ion-etched laminar holographic grating was measured at near-normal incidence in the 14.5-16.0-nm wavelength range. The grating had an electron-beam-evaporated Mo/Si multilayer coating matched to the grating groove depth. The efficiency peaked at 16.3% in the first inside order at 15.12 nm and 15.0% in the first outside order at 14.94 nm. These are believed to be the highest efficiencies obtained to date from a multilayer-coated laminar grating at near-normal incidence in the EUV (lambda<30.0nm) . Zero and even orders were almost completely suppressed. The grating groove efficiency in the first order approached the theoretical limit of 40.5%.