Researchers say they are finally unraveling the effects of ultrafast lasers that can change material states in attoseconds—one-billionth of one-billionth of a second—the time required to complete one light wave’s optical cycle.
The new Israeli research opens up new avenues for scientists to observe light closely in laboratory settings. Under these conditions, a wave crosses a hydrogen atom in a single attosecond, compared to the time required for light to move from Earth to the Moon.
Beyond its immediate use, the development may drive future speed advancements in communications and computing by increasing researchers’ understanding of high-speed quantum light and matter interactions.
Laser Modified Matter
Scientists have already relied on similar processes for years to convert material from opaque to transparent or from a conductor to an insulator. Still, the speed of the process left it extremely difficult to observe. Now, a team at the Weizmann Institute of Science in Israel, led by Professor Nirit Dudovich, has developed a novel method of attosecond laser observation.
Light slows down as it refracts through matter, a phenomenon most visibly seen in rainbows. When sunlight passes through raindrops, each color bends at a slightly different rate, separating into a spectrum. While materials like glass and water typically exhibit steady refraction patterns, researchers have recently discovered ways to modify these properties using lasers. The changes occur on ultrafast timescales—precisely what the Weizmann Institute team sought to measure.
A New Method for Observing Light-Matter Interaction
“This discovery might lead to the development of the fastest processors possible, which will massively increase the speed at which data is transmitted or processed,” Dudovich said.
Three students working under Dudovich—Omer Kneller, Chen Mor, and Noa Yaffe—devised the new dual-laser method. One laser modifies the material, while the other acts like a slow-motion camera, detecting and recording the change. The modifying beam is the more powerful of the two, using longer pulses to alter the material’s optical delay. The observation laser emits two short attosecond pulses, only one of which passes through the material before both are recombined. The interference pattern created when the pulses meet allows researchers to reconstruct the optical delay.
Quantum Ladders
When electrons gain or lose energy, they move up or down what physicists call an energy ladder, determining how they interact with matter. In quantum mechanics, these energy levels form discrete steps, and the amount of energy involved influences a material’s properties. Intense lasers can reshape these ladders—merging two levels into one or splitting one into two.
The new method enables scientists to map the electron’s journey through these varying energy levels by measuring the delay between the two laser pulses. Identifying the electron’s path reveals how the laser altered the material. In this study, the Weizmann Institute team focused only on how single atoms responded to laser manipulation. However, future applications could extend the technique to explore interactions between light and more complex materials.
“Once we can track the ‘journeys’ of single electrons between energy levels, we can use light to control the properties of a material deliberately and precisely, within hundreds or even dozens of attoseconds,” Dudovich said.
“This ability might lead to the development of the fastest processors possible, which will massively increase the speed at which data is transmitted or processed,” Dudovich added. “Our new method also has ramifications for basic research: We hope that it will help us create snapshots of electrons in motion, revealing a variety of previously inaccessible quantum phenomena.”
The paper “Attosecond Transient Interferometry” appeared on November 1, 2024, in Nature Photonics.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.