“The laser field was just beginning then and I was captivated by all the practical applications,” says Mourou, a professor at École Polytechnique in Paris. “I wasn’t able to conceive then of all that we could achieve with lasers but even then I was impressed by its potential.”

Mourou shares the 2018 Nobel Prize in Physics with Donna Strickland, an associate professor at the University of Waterloo in Ontario, his PhD student at the time. They each received a quarter of the prize for the Chirped Pulse Amplification (CPA) technique that paved the way for the shortest, most intense laser beams ever created. The other half of the Physics Prize was awarded to Arthur Ashkin for a separate invention in the field of laser physics.

Mourou and Strickland discovered CPA in the mid-1980s at the University of Rochester. Their revolutionary article was published in 1985 and today it enables doctors to perform millions of corrective laser eye surgeries every year.

CPA made possible the amplification of short laser pulses (approximately a few dozen femtoseconds; 1fs = 10-15 s) to extremely high peak power, equal to petawatt (1015 watt). As Morou explains, the idea is to temporarily spread an ultra-short pulse by means of an optical network in order to reduce its actual intensity before magnifying it. The pulse is then recompressed to reach intensities that are impossible for a conventional amplification to reach.

The CPA technique revolutionized the laser science field and found new applications in different branches of physics, including nuclear and particle physics. Within the medical field, it led to new advances in refractive eye surgery and the treatment of cataracts.

The problem that he and Strickland confronted, as they began work on CPA, Mourou says, was that “the power of the laser was reaching a plateau at a certain level as the laser intensity was too high. When the intensity got too high, it would break down the amplifier and optical component in your laser. But we knew that wasn’t the end of the story. We found a way to circumvent the problem and trick Mother Nature.”

He likens CPA to “having the perfect scalpel, which was for me the eureka moment. We immediately saw its power and that it triggered many possibilities for the laser. We could do things we couldn’t do before.”

The highest achievement

While Mourou knew that he and Strickland were onto something special thirty years ago, he says he never imagined that one day he would be seated between Queen Silvia and Princess Sofia of Sweden at the Nobel Prize Banquet at the Stockholm Concert Hall.

“This is the highest achievement you can obtain as a scientist or even as a human being,” Mourou says. “Science always drove me, the idea that there was something more I could do in the future to surpass what I had previously achieved. I love science. It is what I’ve always wanted to do with my life.”

Born in Albertville, France, in 1944, Mourou completed a degree in physics from the University of Grenoble in 1967 followed by a PhD in 1973 from Paris VI. Following his PhD and a few years into his professional career, Mourou went to the University of Rochester in the US, before heading to the University of Michigan, Ann Arbor, where he became founding director of the Center for Ultrafast Optical Science in 1991. In 2004, Mourou returned to France to the Applied Optics Laboratory (LOA – a joint laboratory between ENSTA ParsiTech, the CNRS, and École Polytechnique). 

Prior to the Nobel Prize, Mourou won the prestigious French Legion of Honor award in 2012, the Frederic Ives medal in 2016 from the Optical Society of America, and the Arthur L. Schawlow award in Laser Science from the American Physical Society. 

Pushing towards new horizons

From childhood, there was no uncertainty about his future path, Mourou says. “I always liked physics and math. But I didn’t know when I was young that you could make a career out of physics. I learned as I was studying that it was possible and that I had a talent to do physics.”

Since his return to France, Mourou initiated three major projects in the realm of high-powered lasers: the launch of the XCAN project at École Polytechnique, the Apollon laser in France, and the large, European infrastructure ELI (Extreme Light Infrastructure) that will host the world’s largest lasers in Hungary, Romania, and Czech Republic. He is also director of the International Center for Zetta-Exawatt Science and Technology, affiliated with more than 27 laboratories around the world, which works to anticipate the future of high-powered lasers.

“When I came back from the States in 2005, I wanted to produce really high intensities, the interaction of light with matter at very, very high intensities. That was truly intriguing to me,” he explains. “With my colleagues from the other laboratories, we try to go beyond the horizon of lasers – for the laser pulses, the maximum power and the minimum duration that you can reach.” 

Passion for science is essential

That drive to always reach higher, even when the outcome is uncertain, is what Mourou says a young scientist today needs as his or her most important quality.

“You have to be passionate about it,” he says. “It can be heaven or hell, depending. You can’t know exactly what you’re going to get {in your work} so you can become easily frustrated. If you’re an engineer, and you want to build something, you build it, but science deals with unknowns. You have no idea what you are going to find so you need to adapt to that uncertainty.”

Yet he says, the rewards can be immeasurable, as long as you love what you do. “Science is very rewarding because you have a lot of freedom. You have to like curiosity-driven work and you have to be passionate about it as you will be thinking about it all the time. It’s a huge commitment if you want to be successful.”