<title>New design schemes for x-ray waveguides based on multiple guiding layers and two-dimensional nanostructures</title>

Abstract

Planar x-ray waveguide structures can be used as resonant beam coupling devices to produce a coherent and divergent x-ray line source with cross-sections in the sub-micrometer range. This article reviews the basic x-ray optical properties of such devices and generalizes the principle of resonant x-ray beam coupling to waveguides containing multiple guiding layers. In such a device, several coherent beams of a width on the order of 100 A to 1000 A can be extracted at the end of the waveguide. Besides coherent diffraction and imaging, interferometry with two or more nanometer sized beams can be envisioned. Furthermore this article presents measurements of the internal reflection of an excited x-ray waveguide mode in a synthetic nanostructure defined by e-beam lithography. In this device the x-ray beam is first coupled into a conventional vertical thin film waveguide structure and then reflected laterally at the quasi one-dimensional edge of the waveguiding layer. The reflectivity of the quasi one-dimensional interface has been recorded under simultaneous excitation of the (vertical) waveguide mode. This experiment constitutes an important step towards the production of a coherent, nanometer sized x-ray point source by two-dimensionally defined waveguide structures.

1D and 2D X-ray waveguides: Optics and applications

“…Complementing other cohérent focusing elements like Fresnel zone plates, Bragg Fresnel lenses, or bent crystal optics, we discuss récent advances in x-ray waveguide optics. leading to beam cross sections determined by the width W of the guiding layer, ranging from several 100 down to 10 nm [7]. Such beam with a cross section in the range between 10-100 nm could open up a whole new range of applications in scattering, microscopy and spectroscopy.…”

Reflection of waveguided X-rays in two-dimensional nanostructures

“…Furthermore, X-ray diffraction with a spatial resolution of $100 nm in one dimension has been demonstrated (Di Fonzo et al, 2000). We have recently shown that even beam widths of less than 100 A Ê can be achieved by the use of X-ray waveguides in the socalled resonant beam coupling devices (Pfeiffer et al, 2001).…”

Advanced x-ray multilayer waveguide optics

“…Tapered waveguides channels with an exit size down to 16.5 nm × 14.6 nm have been reported recently [23]. In [30,31], the single guiding film was generalized to an array of planar wavguides, and in [32,33], the cladding was generalized to a multilayer structure.…”

“…With thin film deposition techniques, notably 8 nm [27,28] for the given material could be reached in a planar thin film waveguide with an optimized cladding material (Mo/C /Mo structure embedded in Ge wafers [29]). Furthermore, the single guiding film [30,31] or the cladding film [32,33] can be generalized to a multilayer structure. Therefore, for purposes of the highest beam confinement or to exploit novel geometries as in this thesis, waveguiding in only one dimension as in an array of thin planar films, is suitable and attractive, owing to a better control of layer sequences.…”