World’s brightest laser illuminates the subatomic realm
At extremely high intensities the way light interacts with matter changes completely, writes Andrew Masterson.
The brightest light ever created by humans has revealed that at high enough intensities the interactions between light and subatomic particles change drastically.
The discovery – by a team led by Wenchao Yan at the Department of Physics and Astronomy at the University of Nebraska-Lincoln, US – potentially opens new possibilities for X-ray imaging and the study of ultrafast nuclear dynamics.
Yan’s team used the university’s Extreme Light Laboratory to focus a laser and create a beam one billion times brighter than the light emanating from the surface of the sun. The light – the brightest thing ever to shine on this planet – was fired into a beam of fast-moving electrons.
The laser pulse lasted for just 30 billionths of one millionth of a second, but that was long enough for the researchers to note several very interesting things.
When less intense light hits an electron, each electron scatters one photon at a time, which exhibits the same energy as it did before the collision. The scattering pattern of photons from electrons is how we see objects.
At extreme intensities, however, the behavior of the electrons changes – and so, too, does the appearance of any object involved.
“When we have this unimaginably bright light, it turns out that the scattering – this fundamental thing that makes everything visible – fundamentally changes in nature,” says team member Donald Umstadter.
The team discovered that at really high levels, the properties of the electrons and photons changed.
Photon trajectories deviated substantially from the predicted direction and speed. Electrons stopped oscillating in a standard up-and-down mode and instead started moving in figure-of-eight formations.
Changed scattering patterns produced changed appearances.
“So it’s as if things appear differently as you turn up the brightness of the light, which is not something you normally would experience,” Umstadter explains.
“An object normally becomes brighter, but otherwise, it looks just like it did with a lower light level. But here, the light is changing its appearance. The light’s coming off at different angles, with different colours, depending on how bright it is.”
The team also noted that a single electron could scatter many photons at the same time, combining their energies to produce a single high-frequency X-ray photon.
The X-rays lasted just billionths of a second, but the team speculates that this could be a very useful property, if harnessed, for example, to produce high-value, highly detailed images of nanoscale structures.