Ferenc Krausz

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Ferenc Krausz

The Hungarian-Austrian physicist Ferenc Krausz and his colleagues have discovered a way to measure the smallest units of time – so small that even processes inside atoms become accessible. The researcher was awarded the Nobel Prize in Physics in 2023 for opening up a world described in incredibly short attoseconds. Significant funding for Krausz's research breakthroughs came from the Austrian Science Fund (FWF).

In laboratories in the basement of TU Wien, Vienna’s university of technology, work often continues well into the night. Without the distractions of day-to-day operations, researchers can concentrate fully on setting up experiments and taking measurements. On one of these nights, on September 8, 2001, to be exact, physicist Ferenc Krausz and his team were at work in a small lab. They were working with highly specialized laser light sources, neon gas, and a variety of control instruments. In the small hours of the morning, when everyone was already exhausted, the breakthrough came: In their experiment, the researchers had demonstrably produced extremely short light pulses in the attosecond range. An attosecond is so short that it can be used to capture the unimaginably fast movements of electrons orbiting an atomic nucleus – an achievement that until that moment had seemed impossible.

22 years later, Krausz, who is now Director of the Max Planck Institute of Quantum Optics in Garching near Munich, was back in his old basement laboratory at TU Wien. He had been awarded the 2023 Nobel Prize in Physics a few days previously, and that successful experiment in Vienna was a key reason for this. Together with his co-laureates Anne L'Huillier and Pierre Agostini, Krausz laid the foundations for observations on previously unattainable time scales. “We can now open the door to the world of electrons. Attosecond physics gives us the opportunity to understand mechanisms that are controlled by electrons. The next step will be to make use of them,” said Eva Olsson, Chair of the Nobel Committee for Physics, about the Committee’s decision.

In a nutshell

Ferenc Krausz’s work was instrumental in establishing attosecond physics, in which extremely short processes in the range of billionths of a billionth of a second can be made measurable. His achievements include the development of a high-energy ultrashort laser in the sub-femtosecond range. Using this technique and with the aid of an effect in the light-matter interaction, the researchers were able to produce and detect attolight flashes. Building on this, Krausz and his team developed a measuring system that uses this approach to investigate electron dynamics in atoms. Based on his research, new areas of work have emerged, such as high-resolution microscopy of living organisms. He has also developed lasers that can be used to diagnose optical diseases and cancer.

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A conversation with Ferenc Krausz

Portrait Ferenc Krausz — From the FWF Wittgenstein Award to the Nobel Prize in Physics: In 2023, Ferenc Krausz was awarded the Nobel Prize in Physics for his breakthroughs in attosecond physics. Several papers funded by the FWF were included on the citation list for the Nobel Prize. © Martin Hörmandinger/ÖAW

Labor TU Wien — In 1996, an FWF START Award provided the Vienna-based physicist with the funds he needed to set up his own research group. The FWF-funded Special Research Area “Advanced light sources (ADLIS)” was established, and Krausz later received the FWF Wittgenstein Award. © TU Wien

Mentor and trailblazer

Born in Mór, Hungary in 1962, Krausz began his scientific career in Budapest, where he studied technical physics and electrical engineering. After coming to TU Wien, he completed his doctorate in quantum electronics in 1991. Even back then, his research focused on ultrashort pulse lasers. He earned his venia docendi in 1993 and was appointed as a full professor in 1999. When talking about his early days in Vienna, Krausz often refers to his mentor Arnold Schmidt. A professor at TU Wien, now retired, Schmidt stood by him over the years as a mentor and trailblazer and provided him with the freedom he needed to succeed. Schmidt would later become long-standing President and Chair of the Supervisory Board of the Austrian Science Fund (FWF).

Krausz’s research work at the time was based on theoretical principles established by his later co-Nobel laureate, the French-Swedish nuclear physicist Anne L'Huillier, among others. In 1996, an FWF START Award provided the Vienna-based physicist with the funds he needed to set up his own research group. The FWF-funded Special Research Area “Advanced light sources (ADLIS)” was created. As early as 1997, Krausz and his colleagues published a paper showing how to generate high-energy laser pulses with a duration of less than five femtoseconds. This work, specifically mentioned by the Nobel Prize Committee in its justification, was funded entirely by the FWF, and was crucial for the later breakthrough.

Ultra-short laser pulses

Femtoseconds are longer than attoseconds by a factor of a thousand. A femtosecond laser would not be enough to actually “look inside” an atom. “Light has a waveform, and the shortest laser flash that nature allows us to generate is roughly one oscillation period, a single wave, so to speak,” explains Krausz in an interview with the German newspaper Die Zeit. “The laser flash cannot be any shorter, because then the wave cannot expand. However, each oscillation period still lasts a few femtoseconds, depending on the color of the light.”

The search for the technology that would give researchers access to the atto-sphere was on. In the successful experiment on that night in September 2001, Krausz and his team fired a femtolaser at neon gas in an attempt to use the light-matter interaction to produce an even shorter light pulse, which has now been made measurable for the first time. If the beam hits a neon atom, it can shoot an electron out of its orbit, which returns to its place after a very short time. During this period, an ultra-short and high-energy quantum of light in the attosecond range is produced, which the researchers have now not only been able to produce, but also detect. In 2001, they published their breakthrough in the scientific journal Nature. In 2002, Krausz recieved the FWF Wittgenstein Award, the youngest winner in the history of the program.

His co-laureate Agostini was also able to present a similar breakthrough almost simultaneously at the Paris-Sarclay research center. Together, they laid the foundation for making previously inaccessible physical processes in the atto range accessible for measurement and manipulation. The human imagination can hardly comprehend the actual length of an attosecond. “There are more attoseconds in one second than there have been seconds since the birth of the universe,” writes the Nobel Prize Committee. Krausz himself provides another comparison in the German journal Welt der Physik: “We know that light can circle our globe ten times in one second,” he writes. “But in an attosecond, light travels less than a millionth of a millimeter.” This distance corresponds approximately to the diameter of a small molecule.

A new look at the quantum world

In 2003, Krausz, who is both a Hungarian and an Austrian citizen, moved on to the Max Planck Institute in Garching. A major development now focused on the use of the attolight flashes for measurements. The researchers applied an old principle that had already been used to measure flashes of light in the 19th century. At the time, a camera known as a smear camera used rotating mirrors to “smear” the beam on a photographic plate, creating a spatial image. The attosecond smear camera, which Krausz credits to co-inventor Paul Corkum of the University of Ottawa in Canada, brings the original femtosecond beam back into play. Its light field is used for measurement in the same way as the earlier mirrors, which ultimately leads to the generation of the high-resolution data needed to track down the processes taking place in attoseconds inside an atom.

The technologies open up a wide range of potential applications, even aside from their immense importance for further research in physics. Krausz mentions computer technology, for example: In this field, the miniaturization of computing chips faces a natural limit. But if in the future, functions like the switching on and off of electricity could be implemented using light technology, the problem of heat generation would be solved and computers could become 100,000 times faster. The Nobel Prize winner himself is heading a project in the field of medicine: The aim is to stimulate molecules in blood samples and find indications of diseases, such as cancer or diabetes, in the resulting signals. Even though these possible applications could hardly have been imagined on that night in September 2001, technology was given a new and incredibly high-resolution sense of time.

Short bio

Born in Mór (Hungary) in 1962, Ferenc Krausz studied electrical engineering at Budapest University of Technology and theoretical physics at Eötvös-Loránd University in Budapest. In 1991, he completed his doctorate in quantum electronics at TU Wien, where he also received his venia docendi just two years later. From 1999 on, he was a professor at TU Wien, and in 2000 he was appointed director of the Center for Advanced Light Sources. In 2003, Krausz became director of the Max Planck Institute of Quantum Optics, where he heads the Attosecond Physics Department. Since 2004, he has also held a chair in experimental physics at the Ludwig Maximilian University of Munich. The experimental physicist was awarded an FWF START Award for his work in 1996, and in 2002 he received the FWF Wittgenstein Award, Austria's most highly endowed research grant.