Light waves, when generated a certain way, can exert twisting forces on matter. In the visible-light regime, such beams have been used as “optical tweezers” to trap and manipulate tiny particles (like a tractor beam) or to detect rotational motion in targets. Now, the ability to generate beams with a specific type of rotational character, known as orbital angular momentum (OAM), has been extended to the soft x-ray regime. The work lays the foundation for a new type of soft x-ray contrast mechanism that could provide access to previously hidden material properties.
In a recently published Nature Photonics paper, researchers from the Advanced Light Source (ALS) and the University of Oregon reported on the fabrication and testing of specialized diffraction gratings that, when placed in the coherent light of ALS Beamline 12.0.2, produce OAM soft x-ray beams of exceptionally high quality.
Image: A flower-like interference pattern generated by a special diffraction grating that superposes two different orbital angular momentum (OAM) modes on a soft x-ray beam.