Anne L’Huillier

Biographical

Anne L’Huillier

I was born in Paris in 1958 and lived the first twenty years of my life in the 13th and 14th arrondissements. My late mother, Yvonne, was first a schoolteacher and then stayed at home to take care of her three children: myself, my sister Françoise, and my brother Jean-Marie. My mother suffered from diabetes from a very early age. As a child, she was told that she could not have children, would become blind, and eventually be amputated. Although she suffered from the consequences of this life-long disease, none of the predictions came true, thanks to progress in science and medicine. This left me with a strong belief in the power of research and science. Her father, Lucien Chrétien, was an engineer and teacher in radio technology. He wrote many books and helped the resistance movement during World War II with radio communications. I don’t remember him, since he died when I was 4, but this family history certainly influenced me as a child, reinforcing this feeling of the importance of science for society. My mother’s family lived in Provins, a small medieval town in Seine-et-Marne, 100 km east of Paris. When my grandfather died, my parents inherited an old smithy in a village called Saint-Hilliers, close to Provins. I have spent almost all my summer vacations there ever since. This small place, among the wheatfields of the Brie region, has remained to this day a much-loved spot.

My late father, Bernard, was an engineer in informatics at a time when computers were huge, rare, expensive, and slow machines. Employed at the CNES (Centre National d’Études Spatiales), he participated in the creation of a computer center devoted to the launch of satellites. He certainly inspired me to pursue a career in sciences, being always a strong supporter. Unfortunately, he passed away four months before the announcement of the Nobel Prize. Many in my family were (or are) talented musicians. I played the flute when I was a teenager and a student. My youngest son is studying to become a professional jazz musician. It is not by accident that I made as many analogies to music as possible during my Nobel Prize lecture when he was present. Finally, I have always enjoyed practicing sports, like skiing, swimming, and playing tennis, wonderful activities which I still do today.

In July 1969, then on vacation in the French Basque region, my grandmother woke me up to watch the first landing on the moon. This was incredibly exciting for a 10-year-old girl with an interest in science. I was amazed by the technology and science that had gone into enabling this endeavor. The fact that it was broadcast live on television to hundreds of millions of people on Earth was also fantastic!    

I had the privilege to go to school in the Quartier Latin in Paris, Ecole Monge, Lycée Montaigne then Lycée Fenelon. These were great places providing a great education! I remember in particular a fantastic teacher in mathematics, who encouraged me to continue in this direction. After the “baccalauréat”, the natural choice for me was to start the “classes préparatoires” in mathematics and physics. After two years of tough work, I was accepted at the Ecole Normale Supérieure (ENS) of Fontenay-aux-Roses in 1977 (the ENS is now in Lyon). The focus of the school fitted very well with one of my goals which was to become a teacher.

At the ENS, I could continue both mathematics and physics and obtained a Master’s degree in both subjects in 1979. The third year at the ENS was the preparation for a national teaching degree called “agrégation”. This was a tough year, especially since the number of positions in mathematics that year (1980) was very low! I was extremely happy to be admitted since it assured me of a teaching position in mathematics. During my fourth and last year at the ENS, I chose to do a DEA (Diplome d’Etudes Approfondies) in quantum physics. This was a fantastic year, with great teachers, like Claude Cohen-Tannoudji and Serge Haroche, who would be awarded the Nobel Prize in Physics in 1997 and 2012 respectively. They made me fall in love with quantum mechanics and atomic physics. Part of the DEA was a two-month internship which I chose to do at the Commissariat à l’Energie Atomique (CEA) in Saclay, in the Service de Physique des Atomes et des Surfaces (SPAS), headed by Claude Manus, in the research group of Gérard Mainfray. The subject was a little exotic, it was about atoms exposed to a strong laser field. Unfortunately, the laser was out of order and the project was reduced to a literature study. However, after this internship, Claude Manus offered me a PhD position, starting in the fall of 1980, which I gladly accepted.

The area of research was atoms in strong laser fields, and the subject of my thesis was the multiple ionization of rare gases by multiphoton absorption. This was my first real encounter with experimental research, and I liked it a lot. I learned, among many things, how to align a laser beam, make an oscillator lase, and safely manipulate oil diffusion vacuum pumps. I worked together with a skilled experimentalist, Louis-André Lompré, and we were helped by dedicated technicians in mechanics and electronics. Data were acquired by taking a photograph of the signal on an oscilloscope screen with a polaroid camera, measuring the signal with a ruler, and writing down the results using logarithmic paper. The thesis work started very well, with results within the first few months and the first article published already in 1982. In the second year of my thesis, Louis-André left for a sabbatical year at Harvard University. I did not get as many results during this second year, but being alone, and responsible for the laboratory, was very educational. When needed I got help from colleagues in the group headed by Gérard Mainfray, called the multiphoton group: Didier Normand and Jacques Morellec working on resonant multiphoton ionization, and Pierre Agostini and Guillaume Petite, working on electron spectroscopy. The main result of my thesis was the identification of two mechanisms for the double ionization of atoms exposed to a strong laser field, sequential and non-sequential. In 1983, in search of a theoretical interpretation of the results of my thesis, I contacted a Swedish theorist, Göran Wendin, a specialist in the description of the photoionization of multielectron atomic systems, who was spending a sabbatical year at the University of Orsay. This resulted in a fruitful collaboration, three theoretical chapters in my thesis (out of six!), several research visits to Gothenburg, Sweden, and a lifelong friendship. I defended my thesis in January 1986. My thesis was one of the last “thèses d’état”. It took me five years, but it immediately gave me the habilitation to supervise theses. 

After my thesis, I spent six months in Gothenburg working on applying diagrammatic many-body perturbation theory and the random phase approximation with exchange to multiphoton ionization. I would spend another brief postdoctoral visit, during the winter of 1988-1989, at the University of Southern California, Los Angeles, in the group of Peter Lambropoulos, using other theoretical approaches for the description of multiphoton processes. In addition to mastering the English language, these two short postdoctoral visits gave me a good foundation in atomic theory, which I have found very useful during my career.

I got a permanent position at the CEA in October 1986. In the summer of 1987, we performed an experiment that had a profound impact on my scientific career. Studying the photon emission from a gas target irradiated by an intense Nd-YAG laser field, we observed odd harmonics of the laser, up to order 33 in argon, and with comparable intensities from the fifth order. I was immediately fascinated by this new process and focused my research on this, both theoretically and experimentally. The theoretical description of high-order harmonic generation (HHG) required solving both the Schrödinger equation, describing the response of an atom to a strong radiation field, and a propagation wave equation. I developed a computer program for solving the second part and collaborated with Ken Kulander and Ken Schafer at the Lawrence Livermore National Laboratory, who were experts in the numerical solution of the time-dependent Schrödinger equation. Again, a fruitful collaboration, with many articles, and lifelong friendships.

A woman and a man in a laboratory
Figure 1. Photograph showing the spectrometer that was specially designed for the observation of high-order harmonics, myself in 1990 and Philippe Balcou, my first PhD student.

In 1989, HHG was not a prioritized subject at CEA. Laser development was on the agenda, thanks to the new Chirped Pulse Amplification technique. I was allowed, however, to continue to work on HHG. I helped supervise a Chinese student, Xiao-Feng Li, designed a new dedicated instrument (see the photograph), and worked on simulations. This was the time when personal computers started to be part of experimental work and I spent a lot of time programming a data acquisition code, which allowed real-time analysis and visualization. In 1990, I had the pleasure of working with a Master’s student, Pascal Monot, and shortly after, with my first PhD student, Philippe Balcou. My previous colleagues Louis-André Lompré and Michel Ferray, who had joined us in 1987, were concentrating on laser development, while I led the research in HHG. To get someone like Philippe Balcou, a bright student from Ecole Polytechnique, as my first PhD student, was a fantastic opportunity! Together, we studied HHG using all available lasers and worked on improving our understanding of the phase matching of the high-order harmonics. Using a Nd:Glass laser newly upgraded with the Chirped Pulse Amplification technique, we could see harmonics with more than 100 eV energy! However, the repetition rate of this laser was 0.1 Hz, and it took many hours to acquire the data.

In the fall of 1992, I was invited together with Philippe, who was then finishing his thesis, and Pascal Salières, who had just started as a PhD student, to perform experiments at Lund University with our dedicated instrument (see above) in collaboration with an enthusiastic Swedish team. Sune Svanberg, Anders Persson, and Claes-Göran Wahlström had just bought the first amplified titanium sapphire laser in Europe, with a 10 Hz repetition rate, and were extremely interested in testing their new laser and facility. Just before we left for Sweden, Maciej Lewenstein began as my first postdoc, working on the theory of high-order harmonic generation. I remember being so embarrassed when welcoming him at the airport, announcing to him that I would leave for Lund for an experimental collaboration. The titanium sapphire laser was perfect for the study of HHG and the experiments in Lund were very successful. Based on our results, Maciej started to develop the Strong Field Approximation that would have a significant scientific impact in the field.

During the same period, I received an invitation to spend half a year at the Lawrence Livermore National Laboratory in 1993, in the group of Michael Perry, which I accepted. Together with Pascal, we spent half a year in California. We worked together with Kim Budil and Todd Ditmire, who were then PhD students of Michael Perry. We were using our instrument, which was flown from Sweden, and a LiSAF laser.

In 1994, I moved to Lund to share my life with Claes-Göran Wahlström. We got married in July 1994. I am very thankful to the CEA, and especially Didier Normand, for their help in the transition period that followed. I did not have a position in Lund, and they allowed me to continue to be employed at Saclay while being there only one week every month. I am also thankful to Pascal Salières, who was writing his thesis at the time, and to Bertrand Carré, who took over the leadership of the HHG activity, for their understanding and friendship. Sune Svanberg, then head of the Atomic Physics division at Lund University, helped a lot during all these years and beyond.

I got a three-year lectureship financed by the Swedish Research Council in 1995. One year later, the Swedish government decided to finance professorships for women to promote gender equality. These were called the Tham professorships, from the name (Carl Tham) of the minister of education and research at the time. In search of a permanent position in Sweden, I applied for a professorship in atomic physics at Gothenburg University, after the retirement of Ingvar Lindgren, and was ranked first. This made it easier for Lund University to open one of these Tham professorships in my research area, and for me, who chose to work in Lund rather than commute to Gothenburg, not to feel too much “positively” discriminated. I became professor in atomic physics at Lund University in 1997.

During my first years in Lund, I had the chance to work with a bright student from the University of Copenhagen, Mette Gaarde. It was a real pleasure to work with a woman for the first time in my career, and we are still in friendly contact. We had regular European collaborations through the access program of what is now called Laserlab-Europe, supported by the European Union. We worked together with Michael Meyer and Mathieu Gisselbrecht on the spectroscopy of excited states of helium using HHG. We had an interesting collaboration with Marco Bellini from the European Laboratory for Nonlinear Spectroscopy (LENS) in Florence, Italy, and Theodor Hänsch from the Max Planck Institute for Quantum Optics in Garching, Germany. We studied the coherence of high-order harmonics and observed experimentally the contributions of the two trajectories mainly responsible for harmonic generation.

I enjoyed working together with my husband Claes-Göran Wahlström for many years until we decided that it was better to be professionally independent: Claes-Göran moved to another research topic, physics at very high laser intensity, while I concentrated on high-order harmonic generation and its applications. Our two sons, Oscar and Victor, were born in January 1999 and April 2000 respectively. It was time for me to have a career break, which I thoroughly enjoyed. I took parental leave, full-time until they reached the age of six months, and then part-time with a decreasing percentage as they got older.

At the beginning of the millennium, I coordinated the European ATTO Marie Curie network. The idea of this network was to demonstrate experimentally the existence of attosecond pulses. Thanks to the experimental results of my co-laureates Pierre Agostini and Ferenc Krausz, the objectives of the network were reached during the first year. The network included all of the European laboratories working on the subject. It was great to exchange ideas and results regularly with all of our colleagues. I am convinced that European instruments such as the Marie Curie networks and training sites contributed a lot to promoting attosecond science in Europe.

I had the great pleasure of being elected to the Royal Swedish Academy of Sciences as a foreign member in 2004, and three years later I was asked to serve on the Nobel Committee for Physics. This was a lot of work and responsibility, during nine years. I learned a lot, and not only in physics.

During the first ten years of the millennium, my emphasis was on increased control of attosecond (as) pulses in a train of pulses. We demonstrated pulses as short as 130 as and explored the additional control provided by a two-color fundamental field. I had great postdocs during this time, like Rodrigo Lopéz-Martens, Thierry Ruchon, and Katalin Varjù, who have since pursued brilliant careers in academia. In 2010, Mathieu Gisselbrecht and I started to explore the idea of measuring the phase across a resonance using attosecond pulse trains, and in 2011, we stumbled on the subject of photoionization time delays, following seminal results by the group of Ferenc Krausz. I supervised excellent students on this subject, for example, Kathrin Klünder, Marcus Dahlström, and David Busto, and initiated long-lasting collaboration with theorists Alfred Maquet from the Université Pierre et Marie Curie in Paris, Eva Lindroth from Stockholm University and Fernando Martín from the University of Madrid, as well as with experimentalists, for example, the group of Raimund Feifel in Gothenborg. We have subsequently explored resonant and non-resonant photoionization in many systems using attosecond interferometric techniques.

In 2008, I obtained my first grant from the European Research Council. It was a great moment! It gave a boost to my research career, making it easier to get other funding. In 2013, I got a grant from the Swedish Research Council for distinguished professors, which meant good funding for 10 years. It was incredible! It helped a lot in reducing the continuous stress of attracting enough external funding to maintain a reasonably sized research group, allowing me to explore new research avenues. During all of my research years in Sweden, I have been supported by the Knut and Alice Wallenberg Foundation with equipment at the Lund High-Power Laser Facility, a Wallenberg Scholar award in 2009, several project contributions, and recently through my participation in the Wallenberg Center for Quantum Technology. From the 2010s, the research group working on attosecond physics in Lund grew from a few people to more than 20. The number of senior scientists working on this topic in Lund increased. Besides myself, Johan Mauritsson and Per Eng-Johnsson became professors. Mathieu Gisselbrecht and Cord Arnold became senior lecturers. Recently Anne-Lise Viotti was recruited as an assistant professor. We work together as independent scientists, each with a different specialty, but try to act as a coherent “attosecond group” toward the outside world.

When I moved to Sweden, I also discovered the pleasure of teaching, which provides a nice balance to research. I have taught optics, laser physics, light-matter interaction, and atomic physics, mostly at the Master’s level. A few years ago, I was asked to teach atomic physics to third-year students in physics engineering. I truly enjoy this course, and it is students from the 2023 intake of this course who were in the lecture room when I received the call from Stockholm: They will always remain special in my memory.

I have received several scientific prizes for my research, and I have been elected to academies as a foreign member in Sweden, the US, Austria, Italy, and France. I will just name a few awards here: The first prize I got was the “Prix Aimé Cotton” in 1990, a prize for young scientists from the French Physical Society. I am convinced that it played a big role in getting my first position in Sweden a few years later. The 1998 Göran Gustafsson Prize, a Swedish prize providing both recognition in Sweden and generous research funding, was important at the beginning of my career in Sweden. The 2011 Unesco-L’Oréal Prize for Women in Science was extraordinary in many respects. The team of journalists that spent a week in Lund to produce a 3-minute video and a few photographs was the most professional I had ever met. I was only moderately happy, however, to see huge photographs of myself at Paris airports, some of them where I was hiding behind laser googles. Who knows? Maybe they encouraged some young women. Recently, the Wolf Prize, the BBVA Award and the Leibinger Zukunftspreis led to unforgettable experiences and memories. To be elected to the French Académie des Sciences, even though I left France thirty years before, touched me a lot and made me very proud! However, nothing prepared me for the incredible recognition brought by the Nobel Prize!

© The Nobel Foundation 2024

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