Astrophysical Phenomena Can Be Studied in the Lab with Record-breaking Laser Pulses

Researchers at the Center for Relativistic Laser Science, Institute for Basic Science in Korea, have achieved a record-breaking laser pulse intensity of more than 10 23 W/cm 2. This laser intensity was completed ten times the time it took by researchers at the University of Michigan. These pulses of ultrahigh-intensity light will allow for exploring complex interactions between light, matter, and light in new ways.

This laser can be used to study phenomena believed to be responsible for high-power cosmic radiations. These rays have energies exceeding a quadrillion electronvolts (eV). Scientists know these rays are from outside the solar system. However, it remains a mystery how and why they form.

“This high-intensity laser will enable us to examine astrophysical phenomena like electron-photon scattering and photon-photon scattering within the laboratory,” said Chang Hee Nam (director of CoReLS) and professor at Gwangju Institute of Science & Technology. It can be used to experimentally test theoretical ideas that were initially proposed nearly a century ago, as well as access them.

The results of years of research to improve the intensity of laser pulses generated by the CoReLS laser are reported in Optica. This is The Optical Society’s journal for high-impact research. Laser matter interactions require a laser beam that is focused precisely. The researchers could focus the laser pulses to just over one micron. This is less than one-fifth of the size of human hair. This new record-breaking laser intensity can be compared to focusing all of the sunlight reaching Earth to the point of 10 microns.

Nam stated that this high-intensity laser will allow us to tackle new and complex science, particularly strong field quantum electrodynamics, primarily dealt with by theoreticians.” Nam said that the laser could help us understand astrophysical phenomena and provide information to enable us to create new sources of radiation treatment using high-energy protons.

Pulses more intense

This new achievement extends the previous work by the researchers, who demonstrated a femtosecond-laser system based upon Ti: Sapphire that can produce four petawatt pulses (PW) for fewer than 20 seconds while being focused on a spot 1 micrometer in diameter. The laser was first reported in 2017. It produced approximately 1,000 times greater than Earth’s electrical power in a laser pulse lasting only twenty quadrillion seconds.

The generated laser pulses must be focused very tightly to produce high-intensity pulses on the target. In this new research, the researchers developed an adaptive optics system that can precisely compensate for optical distortions. The system uses deformable mirrors with a controlled reflective surface shape to correct laser distortions and produce a beam with a well-controlled wavefront. To achieve a very tight focus, they used an off-axis parabolic mirror. This requires careful handling of the focusing optical systems.

Nam stated that Nam’s years of experience developing ultrahigh-power lasers have allowed him to focus the PW laser with a beam size of 28cm to a micrometer spot to achieve a laser intensity exceeding 10 23, W/cm 2.

High-energy processes: A study

Researchers use these high-intensity pulses to generate electrons with energy exceeding 1 GeV (109eV). They also work in a nonlinear regime, in which an electron collides with many hundred laser photons simultaneously. This is nonlinear Compton scattering, a type of solid field quantum electrodynamics that is believed to be responsible for generating highly energetic cosmic rays.

The radiation pressure generated by the ultrahigh-intensity laser will be used to accelerate protons. This process could be used to develop a new laser-based proton source for cancer treatments. Radiation sources used in current radiation treatments require a large radiation shield. Laser-driven proton sources are expected to lower the cost of the system, making them more affordable and, therefore, more accessible to patients.

Researchers continue to find new ways to increase the intensity of the laser without increasing its size. This could be achieved by finding a way to shorten the duration of laser pulses. High-intensity Physics will continue to progress rapidly as lasers capable of reaching peak powers of 1-10 PW and others that go 100 PW are already in use.


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