Scientists generate the highest-intensity laser pulses ever recorded

Scientists in South Korea have achieved a major milestone in physics – and one pursued by researchers in the field for decades – by generating a record-breaking ultra-high intensity laser. The pulse intensity of over 10²³ W per cm sq is the result of a highly advanced optics system that tightly focused the beam on a minuscule target, and opens up entirely new possibilities in research fields ranging from astrophysics to cancer treatments.

The achievement is the work of researchers at South Korea's Center for Relativistic Laser Science (CoReLS), who have been working for more than a decade to better the handiwork of the Hercules laser at the University of Michigan, which previously held the record for the highest intensity laser.

That piece of equipment is capable of producing beams at an intensity of 10²² W/cm², and for almost two decades scientists have been working to one-up it and achieve the elusive goal of a 10²³ W/cm² laser beam. The CoReLS researchers have now accomplished this, through the use of the facility's 4-petawatt femtosecond ultra-high power laser and a highly complex optical system to amplify and focus the beam.

The system includes using a series of deformable mirrors to correct distortions and produce a laser with a tightly controlled wavefront, and then employing a large off-axis parabolic mirror to focus a 28-cm (11-in) laser beam onto a target measuring just 1.1 micrometers wide, which is less than a fiftieth of the diameter of a human hair. The scientists then used a camera and wavefront sensor to image and measure the reflected laser beam, which they say is comparable in intensity to focusing all of the sunlight reaching the Earth onto a spot measuring just 10 microns.

"This high intensity laser will allow us to examine astrophysical phenomena such as electron-photon and photon-photon scattering in the lab," says Chang Hee Nam, director of CoReLS and professor at Gwangju Institute of Science & Technology. "We can use it to experimentally test and access theoretical ideas, some of which were first proposed almost a century ago."

Some of those ideas concern strong field quantum electrodynamics, which are thought to contribute to extremely energetic cosmic rays, while others concern problems a little closer to home. Radiation treatments for cancer today involve high-energy protons produced by accelerators that call for huge radiation shields, but using lasers to produce these protons instead could make these systems less costly, and therefore far more accessible.

"This high intensity laser will let us tackle new and challenging science, especially strong field quantum electrodynamics, which has been mainly dealt with by theoreticians," says Nam. "In addition to helping us better understand astrophysical phenomena, it could also provide the information necessary to develop new sources for a type of radiation treatment that uses high-energy protons to treat cancer."

The research was published in the journal Optica.

Sources: Institute for Basic Science, The Optical Society