A method has been found to create a laser more powerful than the world's highest output laser. It is expected to be used in various fields, such as applying it to laser nuclear fusion research to solve energy-related problems or utilizing it to experimentally verify predictions in advanced theoretical physics.

A team led by Professor Min-seop Hur of the Department of Physics at UNIST (President Yong-hoon Lee), a team led by Professor Hee-yong Suk of GIST (President Ki-chul Lim), and a team led by Professor Jaroszynski of the University of Strathclyde in the UK presented an idea to create laser pulses more than 1,000 times stronger than existing ones through joint research and proved it through computer simulations.

Professor Min-seop Huh of UNIST emphasized, “This research presents a method to overcome the limitations of the ideas of Professor Mourou, who won the 2018 Nobel Prize in Physics, and can be utilized not only in basic sciences such as cutting-edge astrophysics but also in industrial and energy research such as semiconductor lithography and laser nuclear fusion.”

Chirped-pulse amplification (CPA) technology, invented by Professor Morrow in 1985, is a technology that can dramatically increase laser intensity. Currently, utilizing this, it is possible to achieve laser outputs of up to several petawatts (1,000 trillion watts). Considering that the output of sunlight reaching the entire surface of the Earth is only about tens of petawatts, you can understand how powerful a petawatt laser is. However, the scientific community is discussing the need for exawatts, which are more than 1,000 times more powerful, or zettawatts, which are even more powerful.

The ability to produce ultra-high-output lasers, comparable to the output of sunlight reaching the Earth's surface, is achieved by concentrating energy into a narrow space the size of a micron (0.001 mm) while simultaneously compressing it temporally into extremely short pulses of femtoseconds (10⁻¹⁵ seconds). However, if the laser energy exceeds a certain level, the 'diffraction mirrors' used for compression break. The diffraction mirrors required to generate a petawatt laser are approximately 1 meter in size. Conversely, generating lasers of exawat or higher requires diffraction mirrors hundreds of meters in size, which are virtually impossible to manufacture.

The research team solved the problem of laser pulse compression by using plasma instead of diffraction mirrors. Plasma refers to a gaseous state separated into electrons and ions at high temperatures, similar to a lightning flash. Since plasma is an ionized state and is already damaged material, no further damage occurs even when a powerful laser is applied. It also possesses the property of optically dispersing light. In other words, by utilizing plasma in a manner similar to a diffraction mirror, it becomes possible to compress it into a much stronger laser pulse.

"Plasma can act like a conventional diffraction mirror and, as it is a material that is no longer damaged, it can compensate for the shortcomings of existing CPA technology," said Professor Hee-Yong Seok of GIST. "Even plasma only a few centimeters in size could be utilized for ultra-powerful lasers of exawat or higher."

Professor Yaroszinski of the University of Strasclyde stated, “Ultra-high power lasers are an important tool for finding answers to fundamental questions about the nature of the universe, matter, and space-time.”

The results of this study are expected to be used to realize various phenomena predicted in cutting-edge theoretical physics and astrophysics in the laboratory. It can also be applied to laser nuclear fusion research, and is expected to serve as a cornerstone in solving the energy problems facing humanity. The study was published online on November 13 in the globally renowned journal Nature Photonics, and was conducted with support from the Ministry of Science and ICT/National Research Foundation of Korea, the Industrial Innovation Talent Growth Support Program of the UNIST Semiconductor Graduate School, and the UKRI/UK Research Institute for Science and Engineering.