ARCNL researchers report on helical soft-X-ray beams

Controlling the properties of light is of great importance for many areas of physics, including imaging and nanolithography. But for short wavelengths, such as soft-X-ray radiation, such control over especially the phase of light has remained elusive.

02/27/2020 | 6:58 PM

In a paper published in Science Advances, VU/ARCNL researchers Lars Loetgering, Kjeld Eikema and Stefan Witte, together with colleagues from Germany and the USA, report on a method that enables the generation of soft-X-ray beams with controlled orbital angular momentum (OAM). OAM is a property of light in which the phase of a light beam rotates around the beam axis. The VU/ARCNL team now demonstrates that, by inserting a specially designed structure into the beam path, the light can be diffracted in such a way that its OAM properties are modified. Being able to control OAM of light is an important first step; it will give researchers access to the angular structure of the soft-X-ray beam.

Loetgering et al used this new method to generate so-called helical beams of soft-X-ray radiation, in which the intensity distribution of light rotates around its axis upon propagation. They employed a special imaging approach called ptychography to characterize the intensity and phase properties of these helical beams in great detail. Furthermore, they demonstrated the potential of these special beams for high-resolution microscopy, by using them to image a cross-section of an integrated circuit at 30 nanometer spatial resolution.

Figure: 3D-reconstruction of the intensity of a helical soft-X-ray beam as it propagates, as well as a series of cross-sectional images at different propagation distances.