Anne L’Huillier was awarded the Nobel Prize in Physics in 2023 “for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter”. Nearly four decades had elapsed since she first focused infrared laser beams through noble gases, thereby generating high-order harmonics. Over time, her group managed to create light pulses that were only 130 attoseconds long. An attosecond is to a second what a second is to the entire lifespan of the universe. These ultrashort light pulses enable scientists to study extremely rapid processes in matter, where the pulses may be likened to the flash of a camera.

As a Wallenberg Scholar at Lund University, L’Huillier continues her work on developing the attosecond light sources, and on exploring applications. At present, her research team uses four systems to create attosecond pulses with different properties.

“The fourth light source, based on a fairly simple industrial laser, is the newest, developed in collaboration with a Dutch company in the semiconductor industry. Working on this type of source to help the industry is a very exciting step for us,” says L’Huillier.

Four attosecond sources with different properties

High-order Harmonic Generation (HHG) is the technique used for creating attosecond pulses. The four attosecond sources at Lund University are all based on HHG, but they have different properties and are used for different applications. The laboratory Attolab features a standard source, based on a titanium-sapphire laser. It is used to study photoelectrons generated through photoionization, with the aim of understanding their quantum properties. The second laboratory produces attosecond pulses with high energy for a variety of applications, while the third uses an advanced laser system based on what is called Optical Parametric Chirped Pulse Amplification, producing attosecond pulses at an extremely high repetition rate.

The fourth system is the industrial one, where the researchers are exploring a somewhat unexpected application.

“High-order harmonics could be used as a measurement tool of the next generation of computer chips. These days, components on a chip are made as small as just a few nanometers. High-order harmonics will act as a diagnostic beam that can show that everything on the chip is in the right place. It is still at the prototype stage, but if it works, it could become an important technology.”

Still much to discover

This is just one example of how the attosecond pulses could be applied to practical problems. In the future, there will likely be many more.

I have the privilege of having been part of my research field from the very beginning. I’m keen to pass on the knowledge I’ve acquired. I hope to find time to write a book.

“Our work makes it possible to study and even control light-matter interaction in new ways. Examples of applications include a better understanding of complex chemical reactions involving the absorption of light and motion of electrons. But there is a lot of basic research that needs to be done before attosecond pulses may become useful for society,” says L’Huillier.

And there is still a lot to discover about the pulses themselves.

“Indeed, there is! The collaboration we have with the semiconductor industry has demanded more quantitative knowledge on our part. We have had to study the generation of high-order harmonics in a new way. It’s a complex phenomenon with many parameters, and we’re still learning.”

Hectic times as Nobel laureate

Her first year as a Nobel laureate has been a busy one. She has given over 100 lectures to a wide range of audiences, including children, women’s organizations, and academic societies. She has been obliged to turn down many invitations. She is trying to remain involved in her team’s research and has one PhD student left as principal advisor.

“It’s been enjoyable but quite hard work. I realize that it’s good for our field of research, for Lund University, for inspiring young people, especially women. I feel I have to live up to this great honor. It’s a bit silly to think that way, but I can’t help it. And it all requires a lot of energy. So many people want to take a selfie or get an autograph. But if it makes people happy, why not?”

She expects the next few years to be less hectic – perhaps. There are only three living female Nobel laureates in physics. This may be one reason why, in her second year after receiving the prize, she has almost as many bookings as in the first. She prioritizes local and Swedish inquiries, followed by those from the country of her birth, France, and from the rest of Europe. Then comes the rest of the world. She prefers to travel by train because she worries about the health of the planet, but sometimes she has to compromise a little.

“Being a Nobel Prize laureate really is like having a new job – a job to find time for in parallel with other work.”

Text Lisa Kirsebom
Translation Maxwell Arding
Photo Kennet Ruona