Generation and characterization of focused helical x-ray beams

Abstract

The phenomenon of orbital angular momentum (OAM) affects a variety of important applications in visible optics, including optical tweezers, free-space communication, and 3D localization for fluorescence imaging. The lack of suitable wavefront shaping optics such as spatial light modulators has inhibited the ability to impart OAM on x-ray and electron radiation in a controlled way. Here, we report the experimental observation of helical soft x-ray beams generated by holographically designed diffractive optical elements. We demonstrate that these beams rotate as a function of propagation distance and measure their vorticity and coherent mode structure using ptychography. Our results establish an approach for controlling and shaping of complex focused beams for short wavelength scanning microscopy and OAM-driven applications.

Spatial coherence control and analysis via micromirror-based mixed-state ptychography

“…In this work, we use ptychography [19], a lensless imaging and wavefront sensing technique, for spatial coherence analysis. Ptychography has been demonstrated for label-free, quantitative phase imaging (QPI) [20,21], and beam characterization [22,23,24,25,26,27,28], with added benefits through various self-calibration methods [22,29,30,31]. An important extension is mixed-state ptychography, which uplifts the problem of fully coherent wavefront sensing to the computationally more complex problem of characterizing multiple incoherent contributions in a spatially partially coherent beam [32].…”

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

“…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.…”

Observation of magnetic helicoidal dichroism with extreme ultraviolet light vortices

“…Over the last decade, the development of highly coherent sources and tailored optical schemes has opened new possibilities for generating structured light vortices in the extreme ultraviolet (XUV) [12][13][14][15][16][17][18][19] and x-ray [20][21][22][23][24][25] regimes, paving the way to their spectroscopic applications. In this context, magnetic helicoidal dichroism (MHD) has been recently predicted [36], in analogy to the SAM dependent magnetic circular dichroism (MCD).…”