Refractive hard x-ray vortex phase plates

Abstract

In this letter we report on the creation of hard X-ray beams carrying orbital angular momentum of topological charge −h and −3h at a photon energy of 8.2 keV via spiral phase plates made out of fused silica by ultrashort-pulsed laser ablation. The phase plates feature a smooth phase ramp with 0.5 µm nominal step height and a surface roughness of 0.5 µm. The measured vortex beams show sub-micrometer sized donut rings and agree well with numerical modeling. Fused silica phase plates are potentially suited to manipulate the electromagnetic field in highly intense X-ray beams at X-ray free-electron laser sources.

Hard x-ray photoelectron spectroscopy: a snapshot of the state-of-the-art in 2020

“…This was achieved by using spiral phase plates made from fused silica. [335] Whilst we may still have to wait some time for OAM-dependent HAXPES to become a reality, proof-of-principle studies observing an OAM-dependent dichroic photoelectric effect in He atoms are encouraging. [336] 3.3.…”

Effect of the electron motion on the Compton scattering of a twisted photon

“…In fact, the opening angles of twisted photons typically produced in experiments are small ( 1 • ), so that much of this range currently remains inaccessible. However, the field of x-ray optics is advancing rapidly [47,48], including the shaping of twisted beams [49,50], and the technical challenges to produce high-energy twisted photons with large ( 1 • ) opening angles are likely to be overcome in the future. Ultimately, however, the use of small opening angles in the calculations do not alter the main results of this paper.…”

“…However, by adapting the diffraction optics used to generate twisted electrons, recent experiments at the Advanced Light Source [49] report on the development of special diffraction gratings that can directly generate superposition states of twisted soft x rays from a beam operating between 400 eV and 1.3 keV. Another recent study [50] reports on the development of specially designed spiral phase plates to create hard x-ray beams with an energy of 8.2 keV carrying orbital angular momentum, whereas another group [48] reports on the direct generation of Bessel beams up to 15 keV with a refractive x-ray axicon. These studies suggest that further progress in x-ray optics will make it possible to produce superpositions of twisted beams of moderately high energy (∼100 keV) in the future.…”

Hard X-ray wavefront correction via refractive phase plates made by additive and subtractive fabrication techniques

“…However, a constant evolution of these techniques offers not only the capability to fabricate lenses but also the freedom to produce almost any shape. Thus, new refractive optical elements for aberration correction (Sawhney et al, 2016;Seiboth et al, 2017;Laundy et al, 2019) and wavefront manipulation (Seiboth et al, 2019) have emerged. They provide an alternative to deformable mirrors (Mimura et al, 2010) and differential deposition methods (Matsuyama et al, 2018) for wavefront correction as well as to diffractive elements (Vila-Comamala et al, 2014;Loetgering et al, 2020) for wavefront manipulation.…”