Hard-X-ray Zone Plates: Recent Progress

Abstract

The technology to focus hard-X-rays (photon energy larger than 1–2 keV) has made great progress in the past three years. The progress was particularly spectacular for lenses based on the Fresnel zone plate concept. The spatial resolution notably increased by a factor of three, opening up entirely new domains of application, specifically in biomedical research. As we shall see, this evolution is the result of a painstaking optimization of many different aspects rather than of a single technical breakthrough.

Ultra-high aspect ratio high-resolution nanofabrication for hard X-ray diffractive optics

“…X-ray microscopes capable of mapping material properties, performing tomography and probing various types of samples from computer chips to biological cells in the tens of nanometres resolution have become a powerful scientific tool. However, in the hard X-ray region where penetration lengths are much greater and thicker samples can be studied, it is more difficult to control the wavefront of X-rays with both highefficiency and high-resolution owing to the difficulty in fabricating ultra-high aspect ratio diffractive optics 2 . The ability to fabricate high-efficiency hard X-ray diffractive optics using vertical directionality controlled metal-assisted chemical etching (V-MACE) (Fig.…”

X-Ray Imaging

“…For these reasons, soft X-ray microscopes resort to diffractive optics called zone plates or Fresnel Zone Plates (FZP), which provide excellent focal spots with high spatial resolution and low background. The highest performance reported for an FZP microscope to date reaches 15 nm in spatial resolution and 2 nm in positional accuracy [5]. An FZP is a set of radially symmetric rings which alternates between opaque and transparent ( Figure 6.4).…”

Coherent X-ray Imaging: Bridging the Gap between Atomic and Micro-scale Investigations

“…In the former approach image resolution is limited by the pixel size of the detector and by the size of the X-ray source, which is often not the source itself but a demagnified image of it; in the latter case, resolution and image quality depend on the X-ray optical elements. However, despite impressive progress in manufacturing X-ray optics, [9,10] the combination of high numerical aperture, which is a requirement for achieving high resolution, with high efficiency and low aberration remains a true challenge.…”