Front-coupling of a prefocused x-ray beam into a monomodal planar waveguide

Abstract

A hard x-ray beam of photon energy E=12.5keV has been focused by a Kirkpatrick–Baez mirror system and coupled into the front side of a single-mode x-ray waveguide. The beam dimensions of 3.8×2.5μm2 in the focus of the mirror system have thus been reduced in one direction to 32nm, corresponding to the guiding layer thickness of the waveguide. At the same time the waveguide acts as a coherence filter and leads to a well-defined intensity distribution with steep tails in the near- and far-field regions. The total flux transmitted by the waveguide exceeded 108 photons/s while no significant contributions of radiation transmitted through the absorbing waveguide cladding have been observed.

Coherent X-ray diffractive imaging on the single-cell-level of microbial samples

“…X-ray waveguides [209,228] are optical elements for preparing quasi point-sources with sizes well below 100 nm in the hard X-ray regime [147,165,221]. Due to the ltering of the coupled X-rays by propagation through the waveguide [91,222], the prepared quasi X-ray point source is ideally suited for X-ray imaging in the holographic regime [89,165]. In addition, the waveguide source can also be used for iterative phase retrieval of isolated biological specimens in two and three dimensions [12 14] by taking advantage of robust phase retrieval in the Fresnel regime [94,241,334,335].…”

“…Ω := number of independent autocorrelation coe cients number of independent object coe cients = 1 2 91) where A Auto denotes the area of the autocorrelation support. Elser and Millane stated that for cases where Ω is large a successful reconstruction is likely but Ω > 1 may already be su cient [74].…”

Advanced x-ray multilayer waveguide optics

“…To describe the theoretical background of hard x-ray waveguides in this section, subsection 1.1.1 first presents the propagation of wave fields in a planar waveguide (WG) [20,25,[34][35][36][37][38][39]. Using the analytical and numerical calculations, the concept of mode propagation inside a guiding layer is shown.…”

“…The fabrication of 2DWGs was improved by Fuhse et al [20], and more recently extended from overgrown polymer channels to air channels capped by wafer bonding techniques [21], serving several different x-ray optical purposes like beam splitting for interferometry [22] and tapered waveguides channels with an exit size of 16.5 nm × 14.6 nm [23] or angular redirections to "bend" xrays [24]. Notwithstanding these successful developments, lithography still lacks the precision to which planar thin films can be fabricated [25]. For example, the theoretical limits for beam collimation was shown and demonstrated to be in the range of 10 nm depending on the material [26].…”

Two-dimensional X-ray waveguides: fabrication by wafer-bonding process and characterization

“…In practice, the fabrication of ultra-narrow apertures or channels presents the most difficult task. Some possible realizations of ultra-small pinholes or slits are planar waveguides with a tunable air gap [6,7], thinfilm structures [8,9] and pinholes fabricated using focused ion beams [10]. The first two-dimensional waveguides were presented in [11] with poly-methyl-methacrylate (PMMA) as core material with a width w between 50 and 300 nm covered by a 6-nm-thick Cr cladding.…”