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An algorithm-based stitching interferometry method was developed for the measurement of mirrors with large radii of curvature, where the single-shot measurement of the surface figure is not possible. The global and adjacent-subaperture stitching algorithms were compared and the influence of the overlap ratio, the effect of the defocusing error, and methods for its reduction were studied. Using the global stitching algorithm, a root mean square repeatability error of the surface measurement of 0.24 nm was achieved. The centerlines of the stitching result showed good agreement with those from the Nanometer Optical Component Measuring Machine.

The optimized design of multilayer-coated blazed gratings (MLBG) for high-flux tender X-ray monochromators was systematically studied by numerical simulations. The resulting correlation between the multilayer d-spacing and grating blaze angle significantly deviated from the one predicted by conventional equations. Three high line density gratings with different blaze angles were fabricated and coated by the same Cr/C multilayer. The MLBG with an optimal blaze angle of 1.0 degrees showed a record efficiency reaching 60% at 3.1 keV and 4.1 keV. The measured efficiencies of all three gratings were consistent with calculated results proving the validity of the numerical simulation and indicating a more rigorous way to design the optimal MLBG structure. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.

Ru/B4C multilayer mirrors are used for hard X-ray monochromators with moderate spectral resolution and high integral flux. To overcome the problem of large compressive stress inherent in Ru/B4C multilayers, a reactive sputtering technique using a mixture working gas of argon and nitrogen with different partial pressures was tested, and the fabricated multilayers had a period of 3 nm. The intrinsic stress was essentially reduced after nitridation and relaxed to zero value at approximately 15% partial pressure of nitrogen in the working gas. Interface roughness was slightly increased which can be caused by the polycrystalline structure inside the nitridated samples. More importantly, the nitridated multilayers showed an enhanced reflectance (67% at 8.04 keV photon energy) as compared with the one fabricated with pure Ar (54%). The structure analysis with transmission electron microscopy and X-ray photoelectron spectroscopy demonstrated that nitrogen incorporated into a multilayer structure was mostly located in the B4C layers forming BN compounds, which suppressed the diffusion of boron, stabilized the interfaces and enhanced the reflectance.

High resolution X-ray diagnosis is a significant method for obtaining ablation-front and trajectory measurements targeting Rayleigh-Taylor (RT)-instability growth in initial confinement fusion (ICF) experiments. In this paper, a novel Kirkpatrick-Baez-type structure, as a kind of essential X-ray micro-imaging apparatus, has been developed that realizes a large field of view (FOV) and images with high resolution and energy response. Zoned multilayer coating technology is applied to the Kirkpatrick-Baez mirrors to transmit two specific quasi-monochromatic light through the same mirror and enables a compact dual-channel structure. This microscope has been assembled in the laboratory and later implemented at the Chinese SG-III laser facility. The characterization results show that this imaging system can achieve a good spatial resolution of 5 µm in a large FOV of 500 µm, while maintaining a strong monochromatic performance with bandwidth of 0.5 keV at 2.5 keV and 4.3 keV respectively.

Short-period (~3.5 nm) Co/C multilayer mirrors are fabricated by the direct current magnetron sputtering technique through the addition of a small proportion of nitrogen (4-15% partial pressure) to the working gas (Ar). The addition of nitrogen has been demonstrated to significantly suppress the interdiffusion of neighboring materials due to the nitridation of carbon layers as compared with the Co/C multilayer fabricated with the use of pure Ar. The optimal partial pressure of nitrogen was found to be 6%. At this pressure, nitrogen provides abrupt interfaces and the maximal peak value (19%) of the s-polarized radiation reflectivity at the 251-eV photon energy and 45° angle of incidence. The p-polarized radiation reflectivity proved to be less than 0.3%, demonstrating high potentialities of the nitridated Co/C multilayers as Bragg polarizers in the 4.5-6.5-nm spectral range.

To develop the high reflectance mirror for the short wavelength range of the water window region (λ 2.42–2.73 nm), Cr/V multilayers with B4C barrier layers are studied. The grazing incidence x-ray reflectometry results show that the multilayer interface widths are significantly reduced down to 0.21–0.31 nm, after the introduction of 0.1 nm B4C barrier layers at both interfaces. The B4C∕Cr∕B4C∕V multilayer with a large number of bilayers of N 300 maintains the same small interface widths while the surface roughness is only 0.2 nm. According to the transmission electron microscope measurements, the layer structure improvement with barrier layers can be attributed to the suppression of the crystallization of vanadium inside the structure. Using the interface engineered multilayer, a maximum soft x-ray reflectance of 24.3% is achieved at λ 2.441 nm, under the grazing incidence of 42&deg

A universal analytical theory of soft x-ray multilayer gratings operating in the single-order regime is developed here. The single-order regime, in which an incident wave excites only the diffracted wave, is characterized by the maximum possible diffraction efficiency tending to the reflectivity of a conventional multilayer mirror. The theory is applied to analysis of different multilayer gratings, including lamella multilayer gratings, sliced multilayer gratings, blazed multilayer gratings, and blazed lamella multilayer gratings. A simple analytical formula that describes the diffraction efficiency of an arbitrary multilayer grating as a function of the wavelength and the incidence angle is deduced. Expressions for the peak value of the diffraction efficiency and the generalized Bragg condition corresponding to the maximum efficiency are obtained. The high accuracy of the deduced analytical expressions is justified by comparison with rigorous numerical calculations. Comparative analysis of different types of gratings is performed. The advantages and disadvantages of different gratings in practical applications are discussed.

We present state-of-the-art high resolution transmission gratings, applicable for spectroscopy in the vacuum ultraviolet (VUV) and the soft X-ray (SRX) wavelength range, fabricated with a novel process using ultraviolet based nano imprint lithography (UV-NIL). Free-standing, high-line-density gratings with up to 10,000 lines per mm and various space-to-period ratios were fabricated. An optical characterization of the gratings was carried out in the range from 17 to 34 nm wavelength using high-harmonic generation in a capillary waveguide filled with Ne, and around 13.5 nm wavelength (from 10 to 17 nm) using a Xenon discharge plasma.