New laser offers high-resolution imaging

By using the brightest ever laser, scientists have created unique X-ray pulses with the potential to generate extremely high-resolution imagery.

Researchers focused laser light to be one billion times brighter than the surface of the Sun and observed changes in light-matter interaction. As a result, unique X-rays that can generate high-resolution imagery were formed, with potential for medical, engineering and scientific use.

The researchers fired their laser at helium-suspended electrons to measure how photons scattered after striking a single electron. Under typical conditions, one electron occasionally scatters one photon of light at a time. Previous laser-based experiments had managed to scatter a few photons from the same electron but in this research the team managed to scatter almost 1,000 photons at a time.

Dr Umstadter, from the University of Nebraska-Lincoln and co-author of the study in Nature Photonics, said: “When we have this unimaginably bright light, it turns out that the scattering – this fundamental thing that makes everything visible – fundamentally changes in nature.”

A photon from light in standard conditions will typically scatter at the same angle and energy it had before striking the electron, no matter how bright the light may be. But above a certain threshold, the experimental laser’s brightness altered the angle, shape and wavelength of scattered light.

“It's as if things appear differently as you turn up the brightness of the light, which is not something you normally would experience,” said Dr Umstadter. “An object normally becomes brighter, but otherwise, it looks just like it did with a lower light level. But here, the light is changing the object's appearance. The light's coming off at different angles, with different colours, depending on how bright it is.”

This occurred partly because the electron changed from its usual up and down spin to a figure of eight flight pattern. As would happen normally, the electron ejected its own photon, jarred loose from the energy of incoming photons, but this ejected photon absorbed the energy of all scattered photons at a given moment, granting it the energy and wavelength of an X-ray.

Due to the ultra-high resolution of these X-rays, they could be used to look for tumours or fractures that would otherwise be missed using ‘normal’ X-rays. It could also be adapted as an ultrafast camera to snapshot electron motion or chemical reactions by atomic and molecular physicists.