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Interview with Dr. Paul Corkum



Journalist: Amy Stewart

Image: National Research Council Canada



AMY: Hello and welcome back to SciSection! I'm your journalist Amy Stewart, for the SciSection radio show broadcasted on CFMU 93.3 FM radio station. We are here today with Dr. Paul Corkum, a professor of physics at the University of Ottawa, a principal research officer at the National Research Council of Canada, and the co-winner of the esteemed Wolf Prize. Thank you for coming on the show today, Dr. Corkum.

DR. CORKUM: Oh thank you, thank you for inviting me.

AMY: So to start us off, give us an introduction of who you are, your education, and your career background?


DR. CORKUM: Well, I'm Paul Corkum. I'm from Saint John, New Brunswick. I don't know if anybody in your audience is from New Brunswick, but I'm from Saint John, New Brunswick. I went to Saint John highschool, where I met a physics teacher which influenced me and that’s why I'm a physicist. So, after Saint John, I went to Acadia University in Nova Scotia, where I did my undergraduate work and then I took off to the big USA, to Lehigh University. It's a modest size university in Pennsylvania, Bethlem as a matter of fact. And I did my PhD, masters and PhD in Bethlehem. And then I came to the National Research Council, where I've sort of been ever since. I'm partly at the University of Ottawa now. So maybe not quite ever since, but in 2008 I made this jump, but I have a lab at the National Research Council, still.

AMY: That's very great, I think our teachers always tend to inspire us when we are picking our career paths.

DR. CORKUM: Oh it's amazing the influence a teacher can have on you, especially at this age. It's amazing, yeah, absolutely.

AMY: So, much of your research focuses on the field of attosecond science, which is a field of physics which you pioneered and contributed to so significantly that you won the Wolf Prize in physics this year. And for those who don't know, the Wolf Prize is a highly prestigious award which rewards achievements in the interest of mankind and friendly relations among people. So Dr. Corkum, what is attosecond second science and what is some of the work and research you have been doing in this field that has led to your winning of the Wolf Prize?

DR. CORKUM: Well let me start out by saying what an attosecond is, cause it will really make your listeners just amazed. So an attosecond is a billionth of a billionth of a second, in other words, take one second and divide it into a billion pieces and then take one of those billion pieces and divide it once more into a billion pieces. So it’s a billionth of a billionth of a second, it's incredibly short. I like to tell people, an attosecond is to a minute as a minute is to the age of the universe, so that’s really short, right, and that’s slightly overstating it, an attosecond is even shorter than that, but not much. I think at that level it’s ok to make an error. So, if you think about it, sometimes you hear about nanotechnology and nanotechnology is about space, not like time. But a nanometer is a billionth of a metre, so we are talking about something a billion times smaller with respect to a second than a nanometer is to a metre, so that’s amazing again. And you might say: "what, nothing ever happens so fast, who cares?". But you know, we're all held together by electrons, everything in us, every molecule, every piece, every chair you sit on, everything is held together by electrons, making bonds and things like that. So electrons are really light, they only go little short distances and the forces on them are really strong. So in other words, we can sit on a chair. So things happen really fast in the world of electrons. And so we study electrons. Do you want me to tell you how to make an attosecond pulse, I can do it by analogy, ok. So I'm from New Brunswick, I told you, right by the ocean. So you can think about a piece of seaweed attached to a rock. And think of the waves coming in. The waves are waves of water in the case of seaweed, in the case of light, it’s a wave of light or it’s a wave of electric forces on a charged particle but it’s a wave. So I'm going to use a wave of light from a laser just like a wave of water and a charge as the seaweed. Now the seaweed, it bounces up and down in the water, they go up and down, it's still attached to the rock but it bounces up and down. And so my electron would like to bounce up and down too, but it's sort of stuck to the atom, so it can't get away. But if I make it strong enough and I pull hard enough I pull it free. And so my electron bounces up just like a piece of seaweed and bounces down and when it bounces down, it bashes into the atom from which it left or the seaweed bashes into the rock from which it left. And in that bash, in that banging into it, it gives out a burst of light and that burst of light is an attosecond. Now that sounds really unlikely to be important, doesn’t it? I mean it seems incredibly unlikely, but it turns out that you can make real pulses out of the fastest things that we as humans can control. And you make them in this way and you can make them bright enough to do important measurements with them. So, that’s how you make an attosecond pulse. So always remember seaweed and next time you go to the Maritimes, take a look at a piece of seaweed and a rock and you'll think about that. So now, what we do well, you might say, let's take a look at an electron, let's bring this electron out and then I'm going to send it back in again, like the seaweed coming out and then coming back on the rock. And that seaweed, if I looked at it really carefully, I would say something about the rock that hit into it, and smashed up this way, all out in different ways. And so I can take a look at the atom from which, or molecule or solid, from which the electron came. I can see something about it and actually it's less obvious to see but I can even see the electron, I can see what it looks like, I can get a picture of it, so maybe you can get sort of a vision of that from the seaweed crashing into the rock and splattering all around and things like that as it comes in. So that’s what we can do, is we can study electrons, we can see them under some circumstances, we can see how fast they move. And well, in a lab there are all kinds of electrons in the centre and the ones that determine the chemistry they're out around the edge, and so we can even study some of the centre ones, so that’s, I mean that’s an awful lot of stuff we can study.

AMY: That's pretty fascinating, I really like the analogy you used, it makes it a lot easier to visualise something that’s so incredibly small and unfathomable that’s definitely a good way to put it. What do you think the future of this field looks like and what are some potential applications of attosecond science?

DR. CORKUM: Oh wow, there's so many different futures. When we started out, so I got this Wolf Prize for work I did sometime ago. When we started it out was something that sort of happened with atoms and it was really short, I knew it was important but it was kind of specialised in some way, you didn't think it was going to be really, really, really important. But over time we learned that, not only atoms but really it could happen in molecules and not only molecules but it happened in solids and so this sort of became almost every material when you radiate with strong light, behaves this way. So, it’s importance kind of grew and grew and grew. So you can study all of these materials, atoms, solids, and molecules, which is just about everything. We can use these short light pulses and in solids, you can sort of go together with some of the other things that we as scientists, not me but other people, are learning to do in solids to make, oh, so you can pattern solids, you can make all kinds of electronics in solids, and so for different reasons we can pattern solids and focus the light, so I think it will be used to study atoms, molecules, and solids, which is about everything. Especially at this very fast time scale and everyone of them there's something fast. But also these provide a platform in which to make better pulses that can be used for other things. One thing that's really interesting to think about is you know, you and I are made up of cells and these cells, they're really small but you know COVID-19 goes into your cell and takes over a system and reproduce itself and give out lots of more antibodies and you might like to know what's happening inside the cell. So maybe we can go inside cells and look really highly precisely at different places in cells and see what's in the centre, what's outside, what's near the mitochondria, things like that. And so maybe there's less obvious things that will also be important from this, because of the source, because of the short wavelength of the source and the very short timescale of the source. So, I mean almost everywhere you look there's a possibility, you don't know where to look first. I'm trying to do some work on the sub cells, so that’s one of the things.

AMY: That's fascinating how it ties into biology and it could have future applications of studying diseases and the inner workings of cells and the human body and all that, that’s very cool when you see different branches of science come together like that.

DR. CORKUM: Well you think about it, you are made up of molecules and atoms, and so there's all kinds of sizes inside your body that go all the way from the size of your body to the size of a mitochondria inside the cell. And so you have the ability to look at each of these scales and this gives an ability to look at the smallest scale in space and in time. Yup, it's amazing isn't it.

AMY: That is very exciting. So for my next question, so, as a researcher and a professor, what has been one of the most important lessons you have learnt over your career?

DR. CORKUM: I don't know if this is a lesson, I mean I guess the way I do science is I sort of have this picture, this image maybe, of where I want to go, and what is important to do in the long run. And then but of course I have to make day to day decisions, you do this experiment, you do that one, or you do that one. You have to select. And so I keep this long term vision but it’s always tactics, which experiments you actually do. But I tell you what is maybe more interesting, let me tell you what I've learned about science from maybe my wife who's a writer. So she had a contract one time to write about a scientific organisation and she went to it, I wasn’t there, she went to it and these scientists she felt were speaking so frankly to each other, and "how do they not insult each other when they spoke to each other", because if you were in a business meeting and you spoke like this, a person would be insulted and go out of the room and never speak to you again. And so I began to think about this and I thought there's a big difference between the world of science and other things. So when you get into a discussion in science you have to say what you think, what you think is right and there's a way to know it's right, did Newton figure it out, or did Einstein figure it, or we will go down and do an experiment or something like that. There's always a right answer almost. And so you learn to listen to other people's views, change your views if you have to because if you don't, you're going to be proven wrong, so you better change them fast. Change your views if you have to and listen and not take offence. And I think in science you sort of learn not to take offence and say things pretty clearly and to listen carefully to what the other person says because they might be right, and you know, make an adjustment. So, I think it’s a different kind of world, otherwise it’s not so much different but in that way it’s a different kind of world than say business, or, my wife is an artist or a writer, than writing for example, where there is no exactly right answer, but in science there's almost always a right answer or a procedure to find out what the right answer is.

AMY: That is some very good advice. I think you make a great point, science is a lot more of a teamwork effort than we kind of realise and that every great discovery and invention is based off ten more and it's with the collaboration with so many people that we get some of the great technology we have today.

DR. CORKUM: Yeah that’s another thing about writers if you like. If you think of great literature but they're always written by individuals, almost always, almost never by a team. I mean almost no science is done by an individual, almost always by a team. And so you have these people, scientists may be isolated people maybe, one thinks of them as less gregarious of people than the arts and I think it's true. But on the other hand they work in a very gregarious profession where discussion and debate and speaking and writing are really a great deal of what it's about. Where writers are gregarious people in an ungregarious profession sitting there day after day in front of their computer and working by themselves.

AMY: There is quite the juxtaposition there. So for my last questions, physics is a very daunting field, so what would you say to encourage students to pursue working in the field of physics?

DR. CORKUM: I think they're only very few ideas in physics. And they are repeated everywhere. I mean I've talked about water waves and I've talked about light waves, and I could give you a good analogy for how attosecond pulses are made. But are you just thinking about going to the coast or going down to the Ottawa river and just imagine the water waves. And I think that’s often the case in physics, that it’s a few simple ideas that are repeated over and over, maybe made seem complicated by mathematics, I don't mean to say that one should leave out mathematics, it gives physics tremendous power because it can use mathematics for anything. But in ideas underlying physics are really simple, really. So, I don't think one should be daunted by physics, physics can seem daunting for the language and its seems daunting because of the mapping under the mathematics. But physics itself, the ideas are simple.

AMY: I think you make a great point, there's probably a lot of patterns that we could analyse and they carry out through the themes of physics but I also think it takes a great teacher like yourself to come up with these analogies to make it seem a lot more realistic. I mean something like an attosecond is so small and unthinkable but when you compare it to something like seaweed and a wave, it seems so much more real and present. Well thank you so much for joining us today Dr. Corkum. It was fascinating to hear about your career and the amazing work that you are doing in physics. Congratulations on your award and I can't wait to see what attosecond science has in store for the future of physics.

DR. CORKUM: Thank you, thank you for calling me.

AMY: That’s it for this week of SciSection! I'm your journalist Amy Stewart and make sure to check our podcast available on global platforms for our latest interviews.