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Boffins twist beams of neutrons into pasta to cook up holograms

Fun but it's probably better for measuring really small things

Holograms created with neutron beams have been demonstrated for the first time by a team of scientists working at the National Institute of Standards and Technology.

The research published this month in Optics Express shows that although neutron holograms are less visually appealing, they can reveal more information about an object's hidden interior than laser holograms can.

Light beams interfering with one another can create the illusion of three-dimensional objects. Waves of light can separate or merge together, producing different patterns based on the relative positions of the waves. The complex interference patterns is what makes holographic images look like they have more depth than flat images.

The team used a spiral phase plate (SPP) made out of aluminum to give neutron waves orbital angular momentum to make incoming beams of neutrons appear like spiral-shaped fusilli pasta.

First, a neutron passes through an interferometer, where it splits into two beams. The bottom beam goes through an SPP, and the twisted light beam recombines with the top beam after passing through a second interferometer before hitting a photographic plate.

New tech ... Top, off-axis method of optical holography of semitransparent objects introduced by Leith and Upatnieks. Bottom, An artistic depiction of the neutron holography experiment (Source)

The individual neutrons changed phase depending on what section of the SPP the beam passed through. As more neutrons are fired through, a hologram of the object slowly builds up on the photographic plate, revealing small details of the object's internal structure.

"Other techniques measure small features as well, only they are limited to measuring surface properties," said team member Michael Huber, coauthor of the paper. "This might be a more prudent technique for measuring small, 10-micron size structures and buried interfaces inside the bulk of the material."

Scientists are always looking for new ways to exploit a material's properties for useful applications. Since neutrons can penetrate deeper into solids, neutron holography could provide them with a way to inspect a material's properties. ®

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