Record-breaking laser pulses allow astrophysical phenomena to be studied in the laboratory


The researchers demonstrated a standard high laser pulse intensity of over 1023 W / cm2 Using Betawatt lasers at the Center for Relative Laser Science (CoReLS), Institute of Basic Sciences of the Republic of Korea. It took more than a decade to reach this laser density, ten times what a team at the University of Michigan reported in 2004. These high-intensity pulses of light will enable the complex interactions between light and matter to be explored in ways that were not possible before.

The powerful laser can be used to examine the phenomena believed to be responsible for high-energy cosmic rays, which have energies in excess of a quadrillion (1015) electron volts (eV). Although scientists know that these rays originate from somewhere outside of our solar system, how they are made and what they are made of has remained an ancient mystery.

“This high-intensity laser will allow us to examine astrophysical phenomena such as electron, photon and photon scattering in the laboratory,” said Chang Hee Nam, CoReLS Director and Professor at Gwangju Institute of Science and Technology. “We can use it to test and experimentally reach theoretical ideas, some of which were first proposed nearly a century ago.”

at VisualIt is the Journal of the Optical Association (OSA) for high-impact research, researchers have presented results of years of work to increase the intensity of laser pulses from CoReLS lasers. Studying laser material interactions requires a highly focused laser beam, and the researchers were able to focus laser pulses to a spot size of just over one micron, less than one-fifty the diameter of a human hair. The new record-breaking laser intensity can be compared to the concentration of all light reaching Earth from the Sun to a spot of 10 microns.

CoReLS lasers

Researchers created high-intensity pulses using a betawatt laser (pictured) at the Center for Relative Laser Science (CoReLS) in the Republic of Korea. This high-intensity laser will allow scientists to examine astrophysical phenomena such as electron, photon, and photon scattering in the laboratory. Credit: Chang Hee Nam, CoReLS

“This high-intensity laser will allow us to tackle new and challenging sciences, especially the strong electrodynamics of the quantum field, which has been mainly dealt with by theorists,” Nam said. “In addition to helping us better understand astrophysical phenomena, it can also provide the information needed to develop new sources for a type of radiation therapy that uses high-energy protons to treat cancer.”

Increase the density of pulses

The new breakthrough extends to previous work in which researchers demonstrated a femtosecond laser system, based on Ti: Sapphire, that produces 4 petawatt (PW) pulses with periods of less than 20 femtoseconds with a focus on a 1 μm spot. This laser, reported in 2017, produced about 1,000 times more energy than all the electrical energy on Earth in a laser pulse lasting only twenty parts a millionth of a second.

To produce high-intensity laser pulses on a target, the generated light pulses must be focused very tightly. In this new work, the researchers applied an adaptive optics system to precisely compensate for optical distortions. This system includes deformable mirrors – which have a controllable reflective surface shape – to precisely correct distortions in the laser and generate a beam with a well-controlled wavefront. Then they used a large off-axis mirror to achieve a very tight focus. This process requires careful handling of the optical focusing system.

The interaction chamber between the laser and the substance

The proton-acceleration laser material reaction chamber, where the focal density is greater than 1023 W / cm2 It is demonstrated by the intense focus of a multi-bitow laser beam with an off-axis parabolic mirror F / 1.1. Credit: Zhang Hee Nam

“Our years of experience gained while developing high-power lasers have allowed us to accomplish the tremendous task of focusing a PW laser with a beam size of 28 cm onto a micrometer spot to achieve a laser density in excess of 1023 W / cm2He fell asleep.

Study high energy processes

Researchers use these high-intensity pulses to produce electrons with energy greater than 1 GeV (109 MeV) and to work in a nonlinear system where one electron collides with several hundred laser photons simultaneously. This process is a type of strong field quantum electrodynamics called nonlinear Compton scattering, which is thought to contribute to the generation of highly energetic cosmic rays.

They will also use the radiation pressure from the high-intensity laser to accelerate the protons. Understanding how this process occurs could aid the development of a new laser-based proton source for cancer treatments. The sources used in radiation therapy today are created with an accelerator that requires a massive radiation shield. The laser powered proton source is expected to reduce the cost of the system, making the proton tumor therapy machine less expensive and thus widely accessible to patients.

Researchers continue to develop new ideas for further enhancing the laser density without significantly increasing the size of the laser system. One way to achieve this is to discover a new way to reduce the laser pulse duration. With lasers with maximum power ranging from 1 to 10 PW now in operation and facilities of up to 100 PW are planned, there is no doubt that high-intensity physics will advance tremendously in the near future.

Reference: “Achieving laser intensity above 1023 W / cm2“By JW Yoon, YG Kim, IW Choi, JH Sung, HW Lee, SK Lee, and CH Nam on May 6, 2021, Visual.
DOI: 10.1364 /optics.420520


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