Effectively generate extreme ultraviolet laser pulse through wake surfing behind the electron beam

3D simulation of how the wake behind the electron beam (purple) and the light pulse (blue and red stripes) surf behind it. The plasma wake shows no electrons in alternating yellow, and green shows the peak of electron density. When the light pulse is located on the boundary, it can continuously obtain energy - the trick is to keep it there. Source: Ryan Sandberg, High Field Science Group

The laser pulse surfing after the electron beam pulse may rise from the visible light to the extreme ultraviolet light, the simulation of the University of Michigan shows.

This method can produce high-energy laser more effectively, even X-ray. 3D simulation shows that the frequency of light increases by 10 times, while 1D simulation increases by 50 times. In principle, researchers said that the energy of the laser pulse could continue to be enhanced by extending the time period that the laser pulse could ride in the electron beam wake.

"Future lasers, including those used to design semiconductor chips for computers, can use this effect to more effectively generate higher-energy pulses," said Alec Thomas, professor of nuclear engineering and radiation science at the University of Michigan.

The ten-fold increase in frequency is enough to convert visible light into extreme ultraviolet radiation, and this method also maintains the alignment of the waves in the initial laser pulse, called coherence. In addition, the energy of the pulse increases with the increase of frequency, making the peak power up to 100 trillion watts.

This is more than the output of the world's power generation capacity, which is only a brief millionth of a second. Researchers predict that this phenomenon can save a lot of energy in semiconductor manufacturing and laser physics laboratories, although they prefer not to estimate much before confirming this discovery through experiments.

Side view of the 3D simulation of the wake behind the electron beam (purple), and how light pulses (blue and red stripes) surf behind it. Source: Ryan Sandberg, High Field Science Group

Researchers at the University of California, Los Angeles and Los Alamos National Laboratory first predicted this effect in 1989, but at that time, before the laser pulse slid out of the position of the plasma wake, only 10% upshift seemed feasible.

Nevertheless, the California team speculated that if it was possible to keep the light on the boundary between the electron and the area without the electron, the pulse could continue to gain energy, or even increase by ten times.

More than 30 years later, the Michigan team found a new way to achieve this goal. The trouble is that the speed of the electron beam and wake is different from that of the laser pulse - even if the light is gaining energy, the plasma will slow down slightly. In order to keep the laser pulse in the correct position, the boundary also needs to move backward relative to the electron beam.

Sandberg and Thomas proposed to achieve this goal by changing the density of the gas through which the electron beam passes. As the gas density decreases, the wake extends further behind the electron beam.

"By doing so, Ryan managed to upshift the frequency 100 times higher than anyone else had done before," Thomas said.
Sandberg and Thomas believe that this method can achieve a tenfold increase in frequency in laboratories such as the Stanford Linear Accelerator Center and the Zeus laser facility of the University of Michigan in the future. In principle, they expect that as long as light stays on the boundary, the wavelength of light will continue to shorten, driving higher energy and frequency.

Source: Halbaumann 9000 scientific razor