Development of zone plates with a blazed profile for hard x-ray applications (original) (raw)

Reflection zone plates for 2D focusing and spectroscopy of hard X-rays

2013

We propose the use of reflection zone plates (RZP) for two main applications: focusing and spectroscopy. A RZP combines three optical properties-reflection, imaging and dispersion-in one optical element. Having been successfully implemented into an X-ray fs-beamline at BESSY II, RZPs could be an important device in upcoming new high brilliance X-ray sources such as Free Electron Lasers (FEL). The reduction of the number of optical elements in a beamline would allow the highest possible transmission and satisfy the purpose of conserving the unique properties of FELs such as their high coherence. 1. Introduction Reflection Zone Plates combine the imaging and focusing properties of lenses with the dispersive character of diffraction gratings. Such optical elements are of high interest for application at present and planning synchrotron facilities. Their implementation allows the reduction of the number of optical elements in a beamline. Less optical components mean less intensity loss. Higher intensity at the experiment normally means more significant results. Therefore, the development of RZPs has been of high interest in the synchrotron community for several years. Takano et al. [1] described the successful application of one-dimensionally focusing (1D) RZPs for hard X-rays at Spring-8. Erko et al. [2, 3] reported about design, fabrication, and application of two-dimensionally focusing (2D) RZPs for the soft and hard X-ray ranges. Promising results were reached for soft X-rays at BESSY II [2]. The fabrication of 2D RZPs for the hard X-ray range is a technological challenge. The minimum zone size in lateral dimension for these devices is in the range of a few dozens of nanometers. These demands can be fulfilled by using e-beam writing. The creation of the third dimension of the RZPs is more complex. The distance between the upper and the lower level is in the range of only about ten nanometers. Standard procedures for the generation of the second structure level are reactive ion etching (RIE) processes. The lateral precision for the etching process should be less than 1 nm. Lateral variations of more than 1 nm can already cause intensity losses of about 10%. Therefore, high precision processes are on demand. Beside RIE, additive processes like metal sputtering can deliver high precision. For the investigation of the best fabrication method, very precise RIE processes were compared with sputtering processes with shorter durations. The goal of this investigation is design, fabrication, and characterization of 2D RZPs for the hard X-ray range. At the beginning, new software for the calculation of zone plate structures has been developed and tested. Using the calculated ASCII-data, the RZP patterns could be written onto a

High-efficiency and low-absorption Fresnel compound zone plates for hard X-ray focusing

Design and Microfabrication of Novel X-Ray Optics, 2002

Circular and linear zone plates have been fabricated on the surface of silicon crystals for the energy of 8 keV by electron beam lithography and deep ion plasma etching methods. Various variants of compound zone plates with first, second, third diffraction orders have been made. The zone relief height is about 10 mkm, the outermost zone width of the zone plate is 0.4 mkm. The experimental testing of the zone plates has been conducted on SPring-8 and ESRF synchrotron radiation sources. A focused spot size and diffraction efficiency measured by knife-edge scanning are accordingly 0.5 mkm and 39% for the first order circular zone plate.

Grazing incidence phase Fresnel zone plate for X-ray focusing

Optics Communications, 1994

A grazing incidence phase Fresnel zone plate (GIPFZP) allowing a considerable broadening of the usable spectral range in comparison with a Bragg-Fresnel zone plate is being proposed as a new type of Fresnel zone plate for X-ray focusing. A 2 Frn wide image of the X-ray source was obtained by the GIPFZP.

Fabrication of Fresnel zone plates for hard X-rays

Microelectronic Engineering, 2007

A method to fabricate gold structures with high aspect ratio is presented. Fresnel zone plates with an outermost zone width of 100 nm and structures of 1 lm height are fabricated. Preliminary focusing results at an X-ray energy of 8 keV are presented and ways to improve the zone plate parameters are discussed.

Germanium-Based Circular Zone Plates for Soft and Hard X-Rays

AIP Conference Proceedings, 2011

Development of a technological basis for the fabrication of diffraction optical elements has been underway at Synchrotron SOLEIL since April 2009. These diffraction focusing elements are: zone plates and condenser lenses for soft x-rays (80-2500 eV), focusing zone plates for hard x-rays (4-24 keV), and diffraction elements working under complete external reflection conditions with elliptical diffraction zones and a topology appropriate to operate at a glancing incidence to fulfill the conditions of total external reflection (energy range 100-1500 eV). This work discusses fabrication of circular germanium-based zone plates and results of numerical calculations of the behavior of zone plates with real topologies under real experimental conditions. The software used for these calculations allows us to take into account the undercut of zones that occurs after plasmachemical etching as well as variations in the zone heights. Such variations could be used to correct or improve zone plate efficiency after electroplating or plasmachemical etching and can be performed by a focused ion beam etching [1] (direct or with active gas assistance). Data preparation and ion beam control for these corrections can be carried out by Nanomaker software (Interface Ltd).

Performance of hard x-ray zone plates at the advanced photon source

AIP Conference Proceedings, 2000

Fresnel zone plates have been highly successful as focusing and imaging optics for "s oft x-ray microscopes and microprobe. More recently, with the advent of third-generation high-energy storage rings, zone plates for the hard x-ray regime have been put to use as well. The performance of zone plates manufactured using a combination of electron-beam lithography and x-ray lithography is described.

Nanometer focusing of hard x rays by phase zone plates

Review of Scientific Instruments, 1999

Focusing of 8 keV x rays to a spot size of 150 and 90 nm full width at half maximum have been demonstrated at the first-and third-order foci, respectively, of a phase zone plate ͑PZP͒. The PZP has a numerical aperture of 1.5 mrad and focusing efficiency of 13% for 8 keV x rays. A flux density gain of 121 000 was obtained at the first-order focus. In this article, the fabrication of the PZP and its experimental characterization are presented and some special applications are discussed.

One-dimensional Grazing Incidence Zone Plate For Focusing Soft X-rays

AIP Conference Proceedings

We have designed and manufactured a grazing incidence FZP having a non-symmetrical one-dimensional zone structure in order to minimize an outermost zone width. The focal spot size obtained by the FZP is determined by the outermost zone width, and which depends on the manufacturing technique. The projected zone width can be decreased as sine function of the incidence angle. Overall dimension of the zone plate is calculated on the basis that the optical pass difference must be the multiple of a half the wavelength. Two dimensional focusing can be conducted by using a pair of them for vertical and horizontal focusing, correspondingly. Another advantage of the device is that the same focal length can be obtained in case of changing the wavelength. In the case of conventional FZP, experiments using variable wavelength, such as micro-EXAFS, are very difficult because the focal length shifts inversely proportional to the wavelength. The focal length shift can be corrected by changing the incidence angle in the case of the grazing incidence FZP. Electron beam lithography and reactive ion etching technique are used to manufacture FZP. Vanadium is chosen as FZP material since it has high etching rate with CF 4 gas.

High-efficiency zone-plate optics for multi-keV X-ray focusing

Journal of Synchrotron Radiation, 2014

High-efficiency nanofocusing of hard X-rays using stacked multilevel Fresnel zone plates with a smallest zone width of 200 nm is demonstrated. The approach is to approximate the ideal parabolic lens profile with two-, three-, four- and six-level zone plates. By stacking binary and three-level zone plates with an additional binary zone plate, the number of levels in the optical transmission function was doubled, resulting in four- and six-level profiles, respectively. Efficiencies up to 53.7% focusing were experimentally obtained with 6.5 keV photons using a compact alignment apparatus based on piezoelectric actuators. The measurements have also been compared with numerical simulations to study the misalignment of the two zone plates.

Hard X-ray focusing by stacked Fresnel zone plates

2007

Stacking technique was developed in order to increase focusing efficiency of Fresnel zone plates at high energies. Two identical Si chips each of which containing Fresnel zone plates were used for stacking. Alignment of the chips was achieved by on-line observation of the moiré pattern from the two zone plates. The formation of moiré patterns was studied theoretically and experimentally at different experimental conditions. To provide the desired stability Si-chips with zone plates were bonded together with slow solidification speed epoxy glue. Technique of angular alignment in order to compensate a linear displacement in the process of gluing was proposed. Two sets of stacked FZPs were produced and experimentally tested to focus 15 and 50 keV X-rays. Gain in the efficiency by factor 2.5 was demonstrated at 15 keV. Focal spot of 1.8 µm vertically and 14 µm horizontally with 35% efficiency was measured at 50 keV. Forecast for the stacking of nanofocusing Fresnel zone plates was discussed.