Scientists Film the Fastest Phenomena in Nature Using Ultrafast Lasers

Imagine being able to flip a material from transparent to opaque, or reshape its properties in less than a billionth of a billionth of a second. Researchers at the Weizmann Institute have developed a way to track these ultrafast changes using a clever method involving synchronized laser pulses.

By watching how light interacts with materials at attosecond timescales, scientists are now able to see how powerful lasers alter the quantum energy levels inside matter. This breakthrough opens the door to the future of lightning-fast computing, precise material control, and even new ways of observing electrons in motion, offering a new frontier for both applied tech and fundamental physics.

Controlling Matter at Light Speed

Turning a material from opaque to transparent, or from a conductor to an insulator, in an instant might sound like science fiction, but it’s quickly becoming reality. In recent years, scientists have used lasers to control the properties of matter at incredibly fast speeds, within just one cycle of a light wave. However, these changes happen on the attosecond timescale (a billionth of a billionth of a second), making them extraordinarily difficult to observe.

Now, in a study published in Nature Photonics, Professor Nirit Dudovich and her team at the Weizmann Institute of Science have developed a groundbreaking method to track these ultrafast material changes. This advancement in attosecond science, the field that explores the fastest processes in nature, could open new doors for technologies such as ultrafast computing and next-generation communications.

Bending Light with Lasers

To understand how this works, consider a rainbow. When sunlight passes through raindrops, it slows down and bends, or refracts. Different colors of light travel at slightly different speeds through the droplets, spreading out to form a rainbow. Normally, we think of materials like glass or water refracting light in a fixed way. However, researchers have discovered that a powerful laser can change how much a material slows down light, and it can do so on incredibly short timescales.

The Weizmann team proposed that if they could measure the tiny, laser-induced delays in how light travels through a material, they could uncover exactly how lasers are able to alter that material’s properties in real-time.

“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.”

Nirit Dudovich

Tracking Material Changes with Attosecond Precision

The development of this new measurement method was led by three research students, Omer Kneller, Chen Mor and Noa Yaffe, from Dudovich’s lab in Weizmann’s Physics of Complex Systems Department.

The method uses two laser beams. The first is a powerful one, made up of relatively long pulses, that modifies the optical delay experienced by light in a given material. The other one emits extremely short attosecond pulses, and functions as a slow-motion video camera of sorts.

These attosecond pulses come in two copies: one that doesn’t interact with the material, serving as a reference, and another that passes through the material, interacting with it and recording the attosecond delays induced by this interaction. When the two copies are ultimately brought together and interfere with one another, this interference enables the researchers to precisely reconstruct the change in the optical delay experienced by light as it passes through the material.

Mapping Electron Journeys in Quantum Systems

In quantum mechanics, a material’s properties are determined by its energy levels, which form a kind of energetic ladder. Electrons can move up or down this ladder by gaining or losing exactly the right amount of energy. A powerful laser changes this ladder by modifying the location of its levels; it can cause two levels to unify into one or it can split a single level into two.

Just like navigation apps such as Waze can predict how long a journey from point A to point B will take via any given route, the new method reconstructs the route that an electron has traveled between the different energy levels by measuring the delay experienced by the attosecond pulses. Analyzing the electron’s journey in turn allows researchers to learn how the energy levels in a material changed in response to the laser. At first the scientists used the method to learn how the laser changed the properties of single atoms. However, they also present theoretical calculations showing that their new method can be used to reveal the interaction between light and more complex materials.

A Glimpse into the Future of Ultrafast Technology

“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 says. “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. 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.”

Light travels from Earth to the Moon in about 1 second; it crosses an atom of hydrogen in 1 attosecond, one-billionth of one-billionth of a second.

Reference: “Attosecond transient interferometry” by Omer Kneller, Chen Mor, Nikolai D. Klimkin, Noa Yaffe, Michael Krüger, Doron Azoury, Ayelet J. Uzan-Narovlansky, Yotam Federman, Debobrata Rajak, Barry D. Bruner, Olga Smirnova, Serguei Patchkovskii, Yann Mairesse, Misha Ivanov and Nirit Dudovich, 1 November 2024, Nature Photonics.
DOI: 10.1038/s41566-024-01556-2

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