Pulse compression by density gradient plasma yields exawatt to zettawatt lasers

20 Nov 2023

Strathclyde, UK, and UNIST and GIST (Korea) researchers use plasma gradient to force photons to “bunch up”.

A new method of creating laser pulses, more than 1,000 times as powerful as those currently in existence, has been proposed by scientists in the UK and South Korea.

The scientists have used computer simulations in joint research to demonstrate a new way of compressing light to increase its intensity sufficiently to extract particles from vacuum and study the nature of matter. To achieve this the three groups have come together to produce a special type of mirror – one that not only reflects pulses of light but compresses them in time by a factor of more than two hundred times, with further compression possible.

The groups from the University of Strathclyde, UK, and UNIST and GIST, both based in Korea, have proposed a simple idea – to use the gradient in the density of plasma, which is fully ionized matter, to cause photons to “bunch”, analogous to the way a stretched-out group of cars bunch up as they encounter a steep hill. They say that this development “could revolutionize the next generation of lasers to enable their powers to increase by more than one million times from what is achievable now.”

The new method of compressing laser pulses in plasma is described in Nature Photonics.

Peak powers

The highest power lasers in the world have a peak power of around 10 petawatts. To put this in context, 173 petawatts of sunshine reaches the Earth’s upper atmosphere, and about one third of this reaches the Earth’s surface.

High power lasers produce pulses of light with durations that are very short – typically several femtoseconds which is achieved using chirped pulse amplification (CPA).

Professor Dino Jaroszynski, of the University of Strathclyde’s Department of Physics, said, “An important and fundamental question is what happens when light intensities exceed levels that are common on Earth. High power lasers allow scientists to answer basic questions on the nature of matter and the vacuum and explore what is known as the intensity frontier.

“Applying terawatt to petawatt lasers to matter has enabled the development of next-generation laser-plasma accelerators, which are thousands of times smaller than conventional accelerators. Providing new tools for scientists is transforming the way science is done. We have set up the Scottish Center for the Application of Plasma-based Accelerator, at the University of Strathclyde, to push applications based on high power lasers forward.”

Professor Min Sip Hur, of UNIST, commented, “The results of this research are expected to be applicable in various fields, including advanced theoretical physics and astrophysics. It can also be used in laser fusion research to help address the energy issues facing humanity. Our combined Korean and UK teams plan to experimentally test the ideas in the lab.”

Professor Hyyong Suk, of GIST, added, "”Plasma can perform a role similar to traditional diffraction gratings in CPA systems but is a material that cannot be damaged. It will therefore enhance traditional CPA technology by including a very simple add-on. Even with plasma of a few centimeters in size, it can be used for lasers with peak powers exceeding an exawatt.”