In 2019, the Institut für angewandte Photonik (IAP) e. V. in cooperation with Nano Optics Berlin (NOB) GmbH and SIOS Meßtechnik GmbH has made an important progress in the technology for precision soft X-ray optics – the development of three-dimensional (3-D) reflection zone plates (RZPs) with diffractive compensation of slope errors. 2-D mapping of spherical and toroidal grating substrates was used for the metrology of their individual profile. Based on these data, the inscribed grating structure, which corrects the slope error distribution, was computed. The correction algorithm has been implemented as a Python script, and first pilot samples of slope error compensated RZPs are in fabrication process. The 3-D device can replace two or three components in an optical scheme and, therefore, reduce absorption losses by several orders of magnitude. Beyond, the fabrication of customized 3-D Fresnel structures on curved substrates promises considerable improvements for efficiency, resolution and energy range in wavelength dispersive applications. As an example, we present simulations for a compact instrument within (150 – 250) eV. Further development of this approach toward commercial availability will enable the design and construction of compact soft Xray monochromators and spectrometers with unique parameters.
The sensitivity of soft X-ray instrumentation for use in spectroscopy and monochromatization in the Hettrick-Underwood (HU) configuration can be significantly enhanced by replacing the common one-dimensional (1-D) variable line space grating by a two-dimensional (2-D), point-focusing reflection zone plate (RZP). To demonstrate the gain in the performance, we present examples of a flat-field spectrometer for the TiO2 fluorescence between about 390 eV and 530 eV and a femtosecond (fs) monochromator for an energy as low as 38.5 eV. In this context, the application to laser-based high harmonic generation (HHG) sources is discussed.
The interest in ultrafast time resolved spectrometry with soft x-rays considerably increased during the last decade mainly because of the development of new ultra-short pulse sources at large scale facilities, X-ray free electron lasers (XFELs) as well as laboratory scale facilities such as laser-produced plasma (LPP), high harmonics generators (HHG), gas jet isolated atto-second X-ray pulse generators (IPP), relativistic oscillating mirror HHG (RHHG) and time-resolved electron-beam micro-analyzers. Fast progress in all areas demonstrated the ability of modern instrumentation even in laboratories, to reach energy ranges of the so-called “water window” and beyond up to 1000 eV with a pulse duration down to several femto-seconds. In opposite to XFEL giants, emitting presently at photon energies up to 20 keV – 30 keV with tremendous power of several GWatt, laboratory sources emit several order of magnitude lower photon flux and need therefore extremely efficient optics for flux and temporal characteristics preservation. Unfortunately, solutions available in UV, such as conical gratings, are no longer applicable in the photon energy range above 200 eV.
Reflection zone plates (RZP) and 2-dimensional variable line spacing (VLS) gratings are serving as a combination of three functions in one optical element (reflection, energy dispersion and focusing). They were used for the development of different types of spectrometers and monochromators with femtosecond time resolution in the soft x-ray energy range. In this paper, we also suggest to combine two identical RZPs placed in opposite orders of diffraction (+1 and -1) for compensation of time elongation of fs soft X-ray pulses down to several fs.
The 2-Dimensional and 3-Dimensional variable line spacing (VLS) gratings based on total external reflection give the
unique possibility for spectroscopy and focusing in application to 4th and 5th generation synchrotron sources. We focus
on the elaboration of novel approaches for design and fabrication of 3D VLS working in the entire energy range, from
THz to hard X-rays. These optical elements have unique combination of properties and can operate at all XUV sources
including Free Electron Lasers (FELs), Energy Recovery Linacs (ERLs) and High Harmonic Generators (HHGs). Such
3D DOEs are able to cover the energy range of up to 20 keV with energy resolution λ/Δλ ≥ 1000 for soft x-ray and λ/Δλ
≥ 10000 for hard x-ray. We fabricate 3D VLS for time-resolved spectroscopy (energy range 100 – 2000 eV, 7500-9500
eV), FELs and ERLs (energy range up to 3 keV), and HHGs (energy range 10 – 200 eV).
The design for a new XUV-Optics Beamline is presented. The collimated plane grating monochromator (PGM-)
beamline at a bending magnet is setup at the BESSY-II synchrotron radiation facility within the framework of the
blazed-grating production facility. Coupled to a versatile four-circle (ten axes) UHV- reflectometer as a permanent end
station the whole setup is dedicated to at-wavelength characterization and calibration of the in-house produced precision
gratings and novel nano-optical devices as well as mirrors, multilayered systems etc. It is also open to external projects
employing reflectometry, spectroscopy or scattering techniques. According to its purpose, this beamline has specific
features, such as: very high spectral purity, provided by two independent high order suppression systems, an advanced
aperture system for suppression of stray light and scattered radiation, a broad energy range between 10 eV and 2000 eV,
small beam divergence and spot size on the sample. Thus this Optics Beamline will become a powerful metrology tool
for reflectivity measurements in s- or p-polarisation geometry with linearly or elliptically polarized light on real optics up
to 360 mm length and 4 kg weight.
X-ray laser facilities are being constructed all over the world: Linac Coherent Light Source (LCLS) in California,
RIKEN X-Ray Free-Electron Laser at SPring-8 in Japan, European XFEL in Germany etc. XFEL is the next-generation
(4th) light source. However, the number of such experimental facilities (SRS and FEL) is quite limited. At the same
time, relatively small vacuum ultraviolet laboratories with impulse sources [High Harmonic Generators (HHG)] allow
one conduct in-house research. This makes the research community directly involved in experiments with time resolution
much wider. The latest radiation sources and modern physical experiments require application of the newest diffractive
elements. Such diffractive elements are required for implementation of experiments with time resolution using
synchrotron radiation sources or high harmonics generators. For example, valence state evolution or molecules
dissociation in time-resolved investigation. Modern experiments like this might require implementation of time
resolution in femto - (10-15) and even atto- (10-18) seconds.
A smart light trapping scheme is essential to tap the full potential of polycrystalline silicon (poly-Si) thin-film solar cells. Periodic nanophotonic structures are of particular interest as they allow to substantially surpass the Lambertian limit from ray optics in selected spectral ranges. We use nanoimprint-lithography for the periodic patterning of sol-gel coated glass substrates, ensuring a cost-effective, large-area production of thin-film solar cell devices. Periodic crystalline silicon nanoarchitectures are prepared on these textured substrates by high-rate silicon film evaporation, solid phase crystallization and chemical etching. Poly-Si microhole arrays in square lattice geometry with an effective thickness of about 2μm and with comparatively large pitch (2 μm) exhibit a large absorption enhancement (A900nm = 52%) compared to a planar film (A900nm ~ 7%). For the optimization of light trapping in the desired spectral region, the geometry of the nanophotonic structures with varying pitch from 600 nm to 800 nm is tailored and investigated for the cases of poly-Si nanopillar arrays of hexagonal lattice geometry, exhibiting an increase in absorption in comparison to planar film attributed to nanophotonic wave optic effects. These structures inspire the design of prospective applications such as highly-efficient nanostructured poly-Si thin-film solar cells and large-area photonic crystals.
Reflection zone plates (RZP), which consist of elliptical zone plates fabricated on a total external reflection mirror surface, can be effectively used to produce a monochromatic x-ray beam and to focus it at photon energies below 1400 eV. However, as RZPs are highly chromatic, they can be designed only for one specific photon energy. We alleviate this problem by using a novel approach: a Reflection Zone Plate Array (RZPA). Here, we report about successful implementation of novel monochromator based on RZPAs for experiments with 100 fs time resolution at the upgraded Femtoslicing facility at BESSY-II. Aiming at minimum losses in x-ray flux up to 2000 resolution, we fabricated and used an RZPA as a single optical element for diffraction and focusing. Nine Fresnel lenses, designed for the energies of 410 eV, 543 eV, 644 eV, 715 eV, 786 eV, 861 eV, 1221 eV and 1333 eV which correspond to the absorption edges of NK, O-K, Mn-L, Fe-L, Co-L, Ni-L, Gd-M and Dy-M, were fabricated on the same substrate with a diameter of 100 mm. At resolution E/ΔE up to 2000 all edges of other elements in that range (400-1400 eV) are covered, too.
Dedicated diffractive VUV- and X-ray optical elements are essential for future developments in synchrotron instrumentation and methods like e.g. time-resolved spectroscopy. The quality of optical components like gratings or diffractive focusing elements matters directly to the results achievable. On the other hand the availability of such optical components is very limited at present. In this contribution we report on the development of new methods of time-resolved x-ray spectroscopy based on novel 3D diffractive optical elements (DOE) with a unique combination of properties. Such optical elements are of highest interest for application in modern synchrotron facilities like Free Electron Lasers (FELs) as well as for laboratory facilities with high harmonic generators (HHG). The project includes theoretical work as well as the development of a dedicated technology, including metrology, to manufacture such type of optics for applications in atomic, molecular and condensed matter physics. The here discussed type of optics was successfully implemented for soft-X-ray-application at the femto-second-slicing beamline at BESSY II storage ring of the Helmholtz Zentrum Berlin. DOE are expected to be important components in beamlines at upcoming new high brilliance X-ray sources such as FELs. The application of DOE`s allows to reduce the number of optical elements in a beamline. Thus allow to provide the highest possible transmission and flux as well as preserving the unique properties of FEL´s, like wave-front and coherence.
At the European X-ray Free Electron Laser facility one‐ or two‐ Si(111) channel (cut) crystal X‐ray monochromator (Kmonochromator) are planned for photon beam based alignment: gap tuning of the undulator segments and phase tuning of the phase shifters during commissioning and maintenance of the undulators. A prototype device has been built using a single channel-cut crystal and was characterized at PETRAIII synchrotron (at P01, which is the only beamline with two undulator segments) by applying different undulator adjustment methods, intended for the European XFEL, that use imaging and intensity detection. This paper presents the setup and the first results from the experimental qualification of the K-monochromator prototype.
This paper presents the outcome of ray tracing simulations for different optical schemes to be setup at the
European X-ray Free Electron Laser facility (XFEL.EU), Germany: one- or two- channel (cut) crystal X-ray
monochromators (K-Mono; using spontaneous radiation) are planned and designed mainly for photon beam
based alignment, which is gap tuning of the undulator segments and phase tuning of the phase shifters during
commissioning and maintenance of the undulators. The coherent SASE (Self Amplified Spontaneous Emission)
radiation will be monitored pulse-resolved by single-shot spectrometers of which two types are investigated: i) a
three element spectrometer, design proposed by Yabashi et al., which consists of a curved focusing mirror,
followed by a flat analyzer crystal and a 2D-detector.ii) a two element spectrometer based on a reflection zone
plate that reflects and focuses in one step, and a 2D-detector (currently under development).
The results of experimental research of x-ray radiation (5-20 keV) passage through capillary structure in a synchrotron radiation (SR) beam of the storage ring BESSY II (Berlin) are presented. The description of experimental setup and researched capillary structure (capillary lens) parameters are given. The procedure of the researched optics adjustment and registration method of the radiation passed through a lens are described. The analysis of experimental data is also given.
The capabilities of the KMC-2 beamline at BESSY for spatially resolved x-ray measurements with micro- and nanometer resolution are reviewed. An application of micro- X-ray fluorescence analysis (μXRFA), micro-extended X-ray absorption fine structure (μEXAFS), micro-X-ray absorption near-edge structure (μXANES) as well as standing wave technique (SWT) as a powerful method for the organic and non-organic samples characterization with synchrotron radiation is discussed.
Mono and poly-capillary optical systems were used for characterization of organic and non-organic samples, by means of μXRFA mapping and μEXAFS and μXANES.
The results of depth resolved tungsten XAFS measurements in a Si/W/Si trilayer embedded in a Au waveguide structure are presented. A depth resolution on the order of 1nm has been achieved.
The concept of the design and fabrication of X-ray diffraction focusing elements is discussed. This concept includes both reflection and transmission types of optics as well as equipment necessary for their fabrication.
Systematic experimental investigations of Bragg-Fresnel gratings are discussed. Gold and nickel masks with periods of 0.4 μm n 5 μm were evaporated on the surfaces of Si  symmetric and asymmetric crystals. These have been used to obtain x-ray diffraction in the energy range of 8000 eV n 8500 eV. A theoretically calculated maximum of diffraction efficiency of the order of 30 % was measured experimentally for gratings with grooves parallel to the beam direction (sagittal gratings). Diffraction effects in the crystalline substrate for the gratings with grooves perpendicular to the beam direction (meridional gratings) limit the diffraction efficiency on the order of a few percent. Experimental data are compared with the theoretical calculations dispersion and efficiency of Bragg-Fresnel gratings.
A raytracing code for zone plates incorporated in the BESSY raytracing program RAY is described. This option allows one to calculate intensity distributions in a focal plane of circular or linear zone plates considering diffraction limited resolution. Zone plate material properties are also taking into account using optical constants data tables. The complete code is available as PC-Windows version.
The first successful tests of a graded crystal x-ray monochromator at BESSY II based on SiGe crystals are reported. The monochromator crystals with Ge concentration gradient of 0.8%/cm along the crystal surface have been tested at the KMC- 2 beamline. The beam from the BESSY II bending magnet with vertical divergence of 0.2 mrad was used. In comparison with conventional Si crystals the enhancement of an energy resolution is 3 - 5 times and, simultaneously, increase of spectral flux density of 4 - 6 times were obtained.
At present the most widespread multilayer structures are those, in which low absorbing layers from light elements (from carbon, in particular) alternate with strong absorbing layers from heavy metals. Recently it became possible to manufacture x-ray multilayer mirrors containing only low absorbing carbon layers with different values of densities and, consequently, dielectric constants. The properties of these carbon/carbon multilayers were experimentally investigated at BESSY in the energy range of 50 - 2000 eV. Such multilayers promise to combine high reflectivity and high resolution.
The performance of a fixed exit double crystal monochromator in terms of stability and reproducibility of the outgoing X- ray beam becomes the crucial point at modern synchrotron beamlines dealt with the high resolution X-ray optics. Due to the high heat load the monochromator crystals have to be cryogenically cooled. The cooling loop of the second crystal may have an impact on the performance of the monochromator. We therefore suggest to use a Si1-xGex single crystal as the first cooled crystal of the monochromator. With that the second crystal is held at room temperature. To verify the proposed solution an experiment was performed where the lattice parameters of pure Si and SiGe crystals as a function of temperature were measured.
We present first experimental data on a novel type of optical element for synchrotron radiation applications in the x-ray region: namely laterally-graded aperiodic crystals on the basis of Si1-xGex alloys. The lattice parameter of such a gradient crystal containing up to some atomic % Ge in a Si single crystal changes nearly linearly along the plate of diffraction. Thus the variation of the Bragg angle of divergent incident light on the crystal can be compensated for. This opens up the possibility to operate a crystal monochromator in nearly crystal limited resolution in the whole energy range above 2 keV at the full vertical divergence without a collimating premirror. Simultaneously the reflected spectral intensity can be increased considerably as compared with a conventional Si-crystal monochromator.
X-ray multilayer supermirrors for the energy range up to 22 KeV have been theoretically studied and experimentally measured with synchrotron radiation. A multilayer mirror with 50 W/Si bi-layers of different thicknesses on an Si substrate has a smooth reflectivity of up to 32% in the whole energy range from 5 KeV to 22 KeV at a grazing incidence angle of 0.32 degrees.
X-ray optical systems based on Bragg-Fresnel multilayer components imaging an electron beam in a storage ring with micrometer resolution are presented. Design concepts are compared to alternative methods, and the aberrations and limits of Bragg-Fresnel multilayer optics are discussed. Experimental results of imaging the BESSY I source with sub 10 micrometer resolution are presented and the development of a compact Bragg-Fresnel multilayer telescope as a BESSY II standard beam monitor is described.
A new type of Bragg-Fresnel multilayer lens (BFML) has been fabricated at IMT RAS and tested at LURE. The idea to combine different diffraction orders of a zone plate in one focal spot introduced by Simpson and Michette has been realized in a BFML with extended aperture. Matching of the two diffraction orders, the first and third, into one focal plane increases the output flux by a factor of two and the spatial resolution in the same order of magnitude.
X-ray spectroscopy with high spectral (up to (Delta) (lambda) /(lambda) equals 10-4) and spatial resolution (up to microns) is discussed. Devices based on crystals, diffraction, and Bragg-Fresnel elements and their application in Z- and X-pinches and laser plasma experiments are observed.
Problems of microelectronics technology applications for diffractive optical elements fabrication have been considered. The results on x-ray diffractive focusing elements are described: amplitude and phase-contrast Fresnel zone plates as well as freestanding gold gratings. The creation of reflected Bragg-Fresnel lenses for soft x-ray range was made on the basis of multilayer x-ray mirrors. Considerable attention was paid to the correction of different distortion factors involved in the electron beam lithography process.
Experimental investigations and special software for the e-beam exposure system gives the possibility of decreasing the influence of proximity effects and field distortion. The results of creating a focusing element for the soft x-ray range are described: amplitude and phase- contrast Fresnel zone plates as well as reflected Bragg-Fresnel lenses on the base of multilayer x-ray mirrors.