Special Issue "Advanced EUV and X-Ray Optics"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Optics and Lasers".

Deadline for manuscript submissions: closed (15 August 2018).

Special Issue Editors

Prof. Dr. Ulf Kleineberg
Website
Guest Editor
Department of Physics, Ludwig-Maximilians-University of Munich, Garching 85748, Germany; Max-Planck-Institute of Quantum Optics, Garching 85748, Germany
Interests: soft X-ray optics/physics; attosecond physics; nanolithography; measurement and control of electron dynamics in nanostructures; ultrafast nano-plasmonics
Dr. Alexander Guggenmos
Website
Guest Editor
Department of Physics, Ludwig-Maximilians-University of Munich, Garching 85748, Germany; Max-Planck-Institute of Quantum Optics, Garching 85748, Germany
Interests: soft X-ray optics/physics; attosecond physics; development of multilayer optics for attosecond XUV/soft X-ray pulses; High Harmonic Generation by few-cycle laser pulses; electron dynamics in condensed matter combining ARPES and RABBITT

Special Issue Information

Dear Colleagues,                

More than a century after the discovery of X-ray radiation by Wilhelm Conrad Röntgen in 1895, short wavelength radiation in the extreme ultraviolet to soft X-ray region (~30 eV–1 keV photon energy) of the electromagnetic spectrum has been developed into an inevitable and unique probe for fundamental research in physics, chemistry, astronomy and life sciences, as well as a driver of technological development, e.g., in advanced microscopy and lithography systems.

Elemental and chemical specificity, nanoscopic spatial resolution and the ability to generate ultrashort electromagnetic pulses in the attosecond (10-18 s) time domain are unique features in this spectral domain, of which exploitation calls for the development of advanced optics.

Grazing incidence or multilayer reflectors, polarizers, diffractive optics, filters and beam splitters, waveguides and combination of such elements have been developed to ever higher standards over the last three decades and today it can be stated that soft X-ray optical elements and optics systems fulfil the most stringent requirements on surface/interface quality, as well as wavefront accuracy, both on sub-nanometer scales.

The very recent activities in the generation of ultra-intense highly brilliant soft X-ray radiation by Free Electron Lasers, attosecond-pulsed radiation by High Harmonic Generation, as well as the development of EUV microscopy and lithography systems aiming towards 1 nm spatial resolution, now calls for new ideas in optics development towards larger radiation hardness and ultimately precise control over spectral amplitude and phase.

This Special Issue of the journal Applied Sciences “Advanced EUV and X-Ray Optics” calls for research articles covering such new ideas and recent advances in the design, development, fabrication and application of EUV and/or soft X-ray optical elements and systems with unprecedented parameters.

Prof. Dr. Ulf Kleineberg
Dr. Alexander Guggenmos
Guest Editors

Manuscript Submission Information

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Keywords

  • Ultrafast optics

  • Chirping

  • Pulse shaping

  • Multilayer mirrors

  • Diffractive optics

  • Design and fabrication of multilayer optics

  • Optimization of multilayer optics

  • Extreme ultraviolet (EUV) and soft X-rays

  • Metrology of multilayer optics

  • Lithography optics

  • Polarizers

  • FEL optics

Published Papers (8 papers)

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Research

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Open AccessArticle
A Shack-Hartmann Sensor for Single-Shot Multi-Contrast Imaging with Hard X-rays
Appl. Sci. 2018, 8(5), 737; https://doi.org/10.3390/app8050737 - 07 May 2018
Cited by 12
Abstract
An array of compound refractive X-ray lenses (CRL) with 20 × 20 lenslets, a focal distance of 20cm and a visibility of 0.93 is presented. It can be used as a Shack-Hartmann sensor for hard X-rays (SHARX) for wavefront sensing and permits for [...] Read more.
An array of compound refractive X-ray lenses (CRL) with 20 × 20 lenslets, a focal distance of 20cm and a visibility of 0.93 is presented. It can be used as a Shack-Hartmann sensor for hard X-rays (SHARX) for wavefront sensing and permits for true single-shot multi-contrast imaging the dynamics of materials with a spatial resolution in the micrometer range, sensitivity on nanosized structures and temporal resolution on the microsecond scale. The object’s absorption and its induced wavefront shift can be assessed simultaneously together with information from diffraction channels. In contrast to the established Hartmann sensors the SHARX has an increased flux efficiency through focusing of the beam rather than blocking parts of it. We investigated the spatiotemporal behavior of a cavitation bubble induced by laser pulses. Furthermore, we validated the SHARX by measuring refraction angles of a single diamond CRL, where we obtained an angular resolution better than 4 μ rad. Full article
(This article belongs to the Special Issue Advanced EUV and X-Ray Optics)
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Open AccessFeature PaperArticle
On the Properties of WC/SiC Multilayers
Appl. Sci. 2018, 8(4), 571; https://doi.org/10.3390/app8040571 - 06 Apr 2018
Cited by 6
Abstract
A study of the materials properties of WC/SiC multilayer coatings is presented. We investigated the dependence of interface and surface roughness, intrinsic stress, microstructure, chemical composition, and stoichiometry as a function of multilayer period and in some cases compared these to W/SiC multilayer [...] Read more.
A study of the materials properties of WC/SiC multilayer coatings is presented. We investigated the dependence of interface and surface roughness, intrinsic stress, microstructure, chemical composition, and stoichiometry as a function of multilayer period and in some cases compared these to W/SiC multilayer systems. The WC/SiC material pair forms multilayers with extremely smooth and sharp interfaces and both materials remain amorphous over a wide range of thicknesses. These properties are desirable for multilayer-based high-resolution diffractive x-ray optics, such as multilayer Laue lenses (MLLs), which require very thick films in which the layer spacing varies considerably. Thermal and structural stability studies show that WC/SiC multilayers have exceptional thermal stability, making this an extremely robust and favorable material pair for MLLs and other multilayer-based X-ray optical elements. Full article
(This article belongs to the Special Issue Advanced EUV and X-Ray Optics)
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Open AccessArticle
Ni-Al Alloys as Alternative EUV Mask Absorber
Appl. Sci. 2018, 8(4), 521; https://doi.org/10.3390/app8040521 - 29 Mar 2018
Cited by 8
Abstract
Extreme ultraviolet (EUV) lithography is being industrialized as the next candidate printing technique for high-volume manufacturing of scaled down integrated circuits. At mask level, the combination of EUV light at oblique incidence, absorber thickness, and non-uniform mirror reflectance through incidence angle, creates photomask-induced [...] Read more.
Extreme ultraviolet (EUV) lithography is being industrialized as the next candidate printing technique for high-volume manufacturing of scaled down integrated circuits. At mask level, the combination of EUV light at oblique incidence, absorber thickness, and non-uniform mirror reflectance through incidence angle, creates photomask-induced imaging aberrations, known as mask 3D (M3D) effects. A possible mitigation for the M3D effects in the EUV binary intensity mask (BIM), is to use mask absorber materials with high extinction coefficient κ and refractive coefficient n close to unity. We propose nickel aluminide alloys as a candidate BIM absorber material, and characterize them versus a set of specifications that a novel EUV mask absorber must meet. The nickel aluminide samples have reduced crystallinity as compared to metallic nickel, and form a passivating surface oxide layer in neutral solutions. Composition and density profile are investigated to estimate the optical constants, which are then validated with EUV reflectometry. An oxidation-induced Al L2 absorption edge shift is observed, which significantly impacts the value of n at 13.5 nm wavelength and moves it closer to unity. The measured optical constants are incorporated in an accurate mask model for rigorous simulations. The M3D imaging impact of the nickel aluminide alloy mask absorbers, which predict significant M3D reduction in comparison to reference absorber materials. In this paper, we present an extensive experimental methodology flow to evaluate candidate mask absorber materials. Full article
(This article belongs to the Special Issue Advanced EUV and X-Ray Optics)
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Open AccessArticle
Development and Characterization of Two-Dimensional Gratings for Single-Shot X-ray Phase-Contrast Imaging
Appl. Sci. 2018, 8(3), 468; https://doi.org/10.3390/app8030468 - 18 Mar 2018
Cited by 3
Abstract
Single-shot grating-based phase-contrast imaging techniques offer additional contrast modalities based on the refraction and scattering of X-rays in a robust and versatile configuration. The utilization of a single optical element is possible in such methods, allowing the shortening of the acquisition time and [...] Read more.
Single-shot grating-based phase-contrast imaging techniques offer additional contrast modalities based on the refraction and scattering of X-rays in a robust and versatile configuration. The utilization of a single optical element is possible in such methods, allowing the shortening of the acquisition time and increasing flux efficiency. One of the ways to upgrade single-shot imaging techniques is to utilize customized optical components, such as two-dimensional (2D) X-ray gratings. In this contribution, we present the achievements in the development of 2D gratings with UV lithography and gold electroplating. Absorption gratings represented by periodic free-standing gold pillars with lateral structure sizes from 5 µm to 25 µm and heights from 5 µm to 28 µm have shown a high degree of periodicity and defect-free patterns. Grating performance was tested in a radiographic setup using a self-developed quality assessment algorithm based on the intensity distribution histograms. The algorithm allows the final user to estimate the suitability of a specific grating to be used in a particular setup. Full article
(This article belongs to the Special Issue Advanced EUV and X-Ray Optics)
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Open AccessArticle
Temporal Response of Ultrafast Grating Monochromators
Appl. Sci. 2018, 8(1), 5; https://doi.org/10.3390/app8010005 - 21 Dec 2017
Cited by 1
Abstract
The temporal response of double-grating monochromators is analyzed considering two effects on the ultrafast pulse given by the configuration. The first effect is the compensation of the pulse-front tilt, i.e., all the rays emitted by the source in different directions at the same [...] Read more.
The temporal response of double-grating monochromators is analyzed considering two effects on the ultrafast pulse given by the configuration. The first effect is the compensation of the pulse-front tilt, i.e., all the rays emitted by the source in different directions at the same wavelength have to travel the same optical path. The second effect is the group delay introduced by the two gratings, i.e., different wavelengths within the bandwidth transmitted by the slit travel different paths. The methodology to calculate the group delay introduced by the double-grating configuration is presented. Some practical design examples are provided to show the design rules and the achieved performances. Full article
(This article belongs to the Special Issue Advanced EUV and X-Ray Optics)
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Open AccessArticle
Micro-Focusing of Broadband High-Order Harmonic Radiation by a Double Toroidal Mirror
Appl. Sci. 2017, 7(11), 1159; https://doi.org/10.3390/app7111159 - 12 Nov 2017
Cited by 8
Abstract
We present an optical system based on two toroidal mirrors in a Wolter configuration to focus broadband extreme ultraviolet (XUV) radiation. Optimization of the focusing optics alignment is carried out with the aid of an XUV wavefront sensor. Back-propagation of the optimized wavefront [...] Read more.
We present an optical system based on two toroidal mirrors in a Wolter configuration to focus broadband extreme ultraviolet (XUV) radiation. Optimization of the focusing optics alignment is carried out with the aid of an XUV wavefront sensor. Back-propagation of the optimized wavefront to the focus yields a focal spot of 3.6 × 4.0 µm2 full width at half maximum, which is consistent with ray-tracing simulations that predict a minimum size of 3.0 × 3.2 µm2. This work is important for optimizing the intensity of focused high-order harmonics in order to reach the nonlinear interaction regime. Full article
(This article belongs to the Special Issue Advanced EUV and X-Ray Optics)
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Review

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Open AccessReview
EUV-Induced Plasma: A Peculiar Phenomenon of a Modern Lithographic Technology
Appl. Sci. 2019, 9(14), 2827; https://doi.org/10.3390/app9142827 - 15 Jul 2019
Cited by 3
Abstract
After a long period of relatively low interest, science related to effects in the Extreme Ultraviolet (EUV) spectrum range experienced an explosive boom of publications in the last decades. A new application of EUV in lithography was the reason for such a growth. [...] Read more.
After a long period of relatively low interest, science related to effects in the Extreme Ultraviolet (EUV) spectrum range experienced an explosive boom of publications in the last decades. A new application of EUV in lithography was the reason for such a growth. Naturally, an intensive development in such area produces a snowball effect of relatively uncharted phenomena. EUV-induced plasma is one of those. While being produced in the volume of a rarefied gas, it has a direct impact onto optical surfaces and construction materials of lithography machines, and thus has not only scientific peculiarity, but it is also of major interest for the technological application. The current article provides an overview of the existing knowledge regarding EUV-induced plasma characteristics. It describes common, as well as distinguishing, features of it in comparison with other plasmas and discusses its interaction with solid materials. This article will also identify the gaps in the existing knowledge and it will propose ways to bridge them. Full article
(This article belongs to the Special Issue Advanced EUV and X-Ray Optics)
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Open AccessReview
Attosecond Pulse Shaping by Multilayer Mirrors
Appl. Sci. 2018, 8(12), 2503; https://doi.org/10.3390/app8122503 - 05 Dec 2018
Cited by 1
Abstract
The emerging research field of attosecond science allows for the temporal investigation of one of the fastest dynamics in nature: electron dynamics in matter. These dynamics are responsible for chemical and biological processes, and the ability to understand and control them opens a [...] Read more.
The emerging research field of attosecond science allows for the temporal investigation of one of the fastest dynamics in nature: electron dynamics in matter. These dynamics are responsible for chemical and biological processes, and the ability to understand and control them opens a new door of fundamental science, with the possibility to influence all lives if medical issues can thereby be addressed. Multilayer optics are key elements in attosecond experiments; they are used to tailor attosecond pulses with well-defined characteristics to facilitate detailed and accurate insight into processes, e.g., photoemission, Auger decay, or (core-) excitons. Based on the investigations and research efforts from the past several years, multilayer mirrors today are routinely used optical elements in attosecond beamlines. As a consequence, the generation of ultrashort pulses, combined with their dispersion control, has proceeded from the femtosecond range in the visible/infrared spectra to the attosecond range, covering the extreme ultraviolet and soft X-ray photon range up to the water window. This article reviews our work on multilayer optics over the past several years, as well as the impact from other research groups, to reflect on the scientific background of their nowadays routine use in attosecond physics. Full article
(This article belongs to the Special Issue Advanced EUV and X-Ray Optics)
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