Nanofocusing parabolic refractive x-ray lenses

Abstract

Parabolic refractive x-ray lenses with short focal distance can generate intensive hard x-ray microbeams with lateral extensions in the 100 nm range even at a short distance from a synchrotron radiation source. We have fabricated planar parabolic lenses made of silicon that have a focal distance in the range of a few millimeters at hard x-ray energies. In a crossed geometry, two lenses were used to generate a microbeam with a lateral size of 380 nm by 210 nm at 25 keV in a distance of 42 m from the synchrotron radiation source. Using diamond as the lens material, microbeams with a lateral size down to 20 nm and below are conceivable in the energy range from 10 to 100 keV.

Hard x-ray scanning microscopy with coherent radiation: Beyond the resolution of conventional x-ray microscopes

“…In addition, the lateral coherence length at the instrument can be adjusted by prefocusing optics. 19 Inside the scanning microscope, the beam is usually focused by a pair of crossed nanofocusing refractive x-ray lenses made of silicon 4,20 but other optics, such as Fresnel zone plates 6 and multilayer Laue lenses 5 can be used, as well. By means of x-ray fluorescence, absorption, and (coherent) scattering, this scanning microscope can image specimens with elemental, chemical, and structural contrast, respectively.…”

Examining resonant inelastic spontaneous scattering of classical Laguerre-Gauss beams from molecules

“…[43][44][45] Also, several groups of researchers around the world have proposed and tested methods for focusing x-rays from modern sources to beam sizes tens to hundreds of nm's across. [46][47][48] While many of these techniques focus on hard x-rays whose energy exceeds that of core electronic transitions, there is no a priori reason why similar techniques cannot be applied in the region of 200-1000 eV.…”

Focusing hard x rays beyond the critical angle of total reflection by adiabatically focusing lenses

“…When analyzing the spatial confinement of x rays inside a waveguide, Bergemann et al 1 conjectured that the numerical aperture of x-ray optics was physically limited to the critical angle of total reflection. Indeed, besides for waveguides, 1 this assumption holds for mirror optics based on total external reflection 2 and refractive x-ray lenses, [3][4][5] limiting x-ray nanobeams to tens of nanometers. 1,4 For x-ray optics based on diffraction, such as Fresnel zone plates, multilayer Laue lenses, or multilayer mirrors, it was shown [6][7][8] that their numerical aperture is not bounded from above by the critical angle of total external reflection.…”

“…A parabolic lens-both nanofocusing 4,17 or adiabatically focusing 12 -has a truncated gaussian aperture function (transmission profile), damping the peripheral amplitudes compared to those on the optical axis. The FWHM size of the Airy disc d t (diffraction limited focus) can be associated to an effective aperture D eff and with it a numerical aperture NA by 22…”

“…On the way to the instrument, the x-ray beam is monochromatized (E ¼ 20 keV) by a Si (111) double-crystal monochromator. In order to focus the x-rays in two dimensions, the AFL was combined with a conventional nanofocusing refractive x-ray lens 4,17 (N ¼ 300, R ¼ 12.4 lm, R 0 ¼ 19 lm) in a crossed geometry as shown in Figure 2. At the entrance of the nanoprobe, the aperture of the optic is defined by a pair of high-precision slits that were set to 10 lm  50 lm (horiz.…”