Paul Corkum talks to Hilary Crichton about attosecond pulses and how developing new ideas is like skiing downhill

Paul Corkum OC, FRS, FRSC is director of the Joint University of Ottawa/National Research Council Attosecond Science Laboratory and a professor of physics at the University of Ottawa. He introduced many of the concepts in strong field atomic and molecular science. His many awards include the Canadian Association of Physicists' gold medal for lifetime achievement in physics and the American Physical Society's Arthur L. Schawlow prize for quantum electronics.

Who inspired you to become a scientist?

It was my high school physics teacher. He believed that he should prove any statement. In my very first physics class, he introduced us to the concept that the dimensions of equations must balance. I remember thinking about this a lot and I liked the idea very much. From then on, I loved the simplicity and beauty of physics.

Tell us about your scientific background.

After high school, I attended an excellent small college, Acadia University, in Canada. There were only undergraduates in the physics department, so I was able to get a summer job in the laboratory every year. These summer positions introduced me to research. I published my first paper as an undergraduate.

Then, I headed to the US to attend Lehigh University, Pennsylvania. After Lehigh, I managed to get a postdoctoral fellowship at the National Research Council (NRC) of Canada, where I have worked until this year. About six months ago, NRC and the University of Ottawa formed a joint laboratory for attosecond science. I am now director of the joint laboratory and I have a faculty position at the university.

You started your career as a theoretician. What prompted the move to experiments?

I made the transition because of the job market at the time. I was offered an experimental position. I was able to make the transition because, in graduate school, I did not have enough money to pay others to fix my car. Instead, I learned to repair my own cars. I rebuilt both the engine and the transmission. After that, experimental work did not seem so intimidating for me. I think equally, NRC felt that any theorist who could rebuild his car would not be too big a risk!

Your research paved the way in producing attosecond pulses. What are you currently using them to investigate?

Many things. Attosecond science has implications everywhere. I will single out one very exciting one that has guided a great deal of my research for the past five years. Attosecond technology opens a class of new methods for imaging molecules. The methods are all fully compatible with measuring chemical and electronic dynamics. The image can be of an orbital, the position of the atoms or both simultaneously. That means that it is possible to see the electronic and nuclear structure of a molecule and watch it change. So far, we have concentrated on diatomic or triatomic molecules but I think we can extend the methods to molecules of more chemical or biological interest.

What's going to be the next big thing in your field?

Combining space and time - attosecond and Ångström. What we have really done so far is to introduce a systematic way to sub-divide the laser cycle - currently the shortest laser pulse is only 1/30 of the period of the light that generated it. Equally, it is possible to sub-divide the light wavelength. If we can systematically achieve a spatial resolution of 1/30 of a wavelength then we have a powerful tool for nanotechnology. Already, for molecular problems, my group resolves one Ångström features. In other words, our spatial resolution is less than one nanometre. Looking further ahead, the methods that we have developed are only the first of many possible methods. In essence, it is the high nonlinearity that leads to attosecond pulses. Other approaches that do not rely on re-collision will surely arise. They will open even shorter timescales. At this point, the horizon seems limitless.

Which piece of research are you most proud of?

The re-collision model [a unique interplay between a coherent electron, coherent atoms or molecules and coherent light] has become the organising concept of a whole sub-field of science. What more can one ask for as a scientist? I am also pleased that I realised its implications almost immediately - for making and measuring attosecond pulses and for imaging molecules.

Which trends in the scientific community are you pleased about?

We are in a golden age of science. Europe has regained its pre-war strength in science. Now, European scientists create new scientific ideas equally with American scientists. Asian science is also advancing rapidly. It bodes well for the future. There is an ever larger pool of talented people ready to concentrate on the world's problems.

What is the most rewarding aspect of your work?

I will single out two things. First, there is nothing more rewarding or exciting than to develop a new idea. I think of it as the intellectual equivalent of downhill skiing. When skiing, you slide down a snow-covered hill as fast as you dare. To me, this is the definition of physical fun. In science, you follow a new idea - one that no one has ever thought about before - with total concentration. To me, this is the highest intellectual satisfaction possible.

Second, I like the interplay between the intellectual and social aspects of science. Most people (including me when I started) think of a scientist's life as isolated - always working alone in the laboratory. In fact, science is just the opposite. Scientists almost always work in teams. They discuss ideas openly and continually. Once they make an advance, it is their job to tell others. To do this, they travel the world. I have scientific friends to whom I am as close as to my neighbours. I have met their families and they mine. From them I gain a unique insight into other countries and other cultures. This, to quote physicist and science writer, Jeremy Bernstein, is 'the life it [science] brings'.

Which scientist, current or historic, do you most admire and why?

Niels Bohr. He was the father of quantum mechanics - arguably the most creative scientific development of the 20th century. After introducing the Bohr model, he built a creative team of young scientists and established an atmosphere of ideas. In this atmosphere, he encouraged a more refined quantum theory to develop, surpassing his original. Under his guidance, a creative new generation of scientists became famous. In the end, our understanding of the universe was profoundly changed. It is quite an accomplishment.

If you had one piece of advice to pass on to young scientists, what would it be?

This is an exciting time in science. Technology is allowing us precision and control that was not possible before. There are opportunities everywhere. My advice to a young scientist: if you have the talent, immerse yourself in the new technology and ideas and follow where your imagination leads you.

How do you spend your free time?

I am a true Canadian. I love winter. Winter brings a unique lifestyle. Ottawa has a canal that runs through the city, which in winter forms a seven kilometre long skating rink, open day and night. Also, the city is on the edge of an old mountain range that is perfect for cross-country skiing. So skating and skiing in Ottawa are probably the best in the world. The summer is also unusual. Wilderness is less than a 30 minute drive from Ottawa. My wife and I can leave work with a canoe on the roof of the car and in 30 minutes be paddling in a secluded lake. That said, it is very hard to get the time to canoe or ski more than a few times each year.

If you weren't a scientist, what would you do?

I would be an economist. I find it to be a physics-like profession.