The 2018 Nobel Prize in physics was awarded Tuesday to Arthur Ashkin, Gérard Mourou and Donna Strickland for their pioneering work to turn lasers into powerful tools.
Ashkin, a researcher at Bell Laboratories in New Jersey, invented “optical tweezers” — focused beams of light that can be used to grab particles, atoms and even living cells and are now widely used to study the machinery of life.
Mourou, of École Polytechnique in France and the University of Michigan, and Strickland, of the University of Waterloo in Canada, “paved the way” for the most intense laser beams ever created by humans via a technique that stretches and then amplifies the light beam.
“Billions of people make daily use of optical disk drive, laser printers and optical scanners … millions undergo laser surgery,” said Nobel committee member Olga Botner. “The laser is truly one of the many examples of how a so-called blue sky discovery in a fundamental science eventually may transform our daily lives.”
Strickland is the first woman to be awarded the physics prize since 1963, when Maria Goeppert-Mayer was recognized for her work on the structure of nuclei. Marie Curie won the physics prize in 1903 and the chemistry Nobel Prize in 1911. A reporter asked the professor what it felt like to be the third woman in history to win the prize.
“Really? Is that all? I thought there might have been more,” Strickland responded, sounding surprised. “Obviously we need to celebrate women physicists because we’re out there. I don’t know what to say. I’m honored to be one of those women.”
Ashkin would not be available for interviews, the committee said Tuesday morning; he was too busy working on his next paper.
In a laser beam, light waves are tightly focused, rather than mixing and scattering as they do in ordinary white light. Since the first laser was invented in 1960, scientists speculated that the energy of these focused beams could be put to work to move and manipulate objects — a real life version of Star Trek’s “tractor beams.”
“But this was science fiction for a very long time,” said committee member Mats Larsson.
Ashkin spent two decades studying the properties of lasers, first recognizing that objects could be drawn toward the center of a beam, where the radiation was most intense. (A committee member demonstrated this phenomenon during the news conference by using a hair dryer to suspend a ping-pong ball in the air.) By further focusing the beam with a lens, he developed a “light trap” that could hold a small spherical object in place.
Ashkin used his new tool to hold a particle in place, then an atom, and eventually, in 1987, a living bacterium. Ashkin even demonstrated that the tool could be used to reach into a cell without damaging the living system.
“That of course was the real breakthrough, that one could manipulate such complex objects,” Larsson said.
Around the same time, Morou and Strickland were working together at the University of Rochester to overcome a problem that had dogged laser research for decades: High intensity laser beams tended to destroy the material used to amplify them. It was as though scientists were trying to boil water in a pot that couldn’t handle such high temperatures.
The Rochester researchers developed an elegant workaround, which they called “chirped pulse amplification.” First they stretched out the beam with a mile-long fiber optic cable, reducing its peak intensity. Then they amplified the signal to the desired level, before compressing it down into an ultra-short, ultra-powerful pulse lasting just a tiny fraction of a second.
“Different people were trying to get short pulses amplified in different ways,” Strickland said. “It was thinking outside the box to stretch first and then amplify.”
Strickland was a graduate student at the time; the 1985 article that announced their achievement was her first scientific publication, according to the Nobel website.
Students have historically not been recognized by the Nobel Committee, something that critics say overlooks the work done by young scientists who are more frequently women and underrepresented minorities.
But graduate students are the backbone of most scientific research; often they run the experiments and do the detailed data analyses that lead to major discoveries. The prize-winning discovery of pulsars — swiftly spinning cores of collapsed stars — would not have been possible without Jocelyn Bell Burnell, who built the telescope and spotted the first signal when she was earning her PhD. But Burnell was not among the list of laureates for that prize.
The magazine Nature reported this weekend that the Royal Swedish Academy of Sciences would explicitly call on future nominators to consider gender, geography and topic for the 2019 prizes.
Secretary General of academy Göran K. Hansson said Tuesday that the academy is taking these measures “because we don’t want to miss anyone. But they did not affect this year’s prize: “It’s important to remember that the Nobel prize is awarded for discoveries and inventions, and those who receive it have made major contributions to humankind, and that’s why they get the prize.”
CPA has been used to take images of split-second processes, such as the interactions between molecules and atoms. It’s also fundamental for laser eye surgery.
“The innumerable areas of application have not yet been completely explored,” the Nobel Committee said in a statement. “However, even now these celebrated inventions allow us to rummage around in the microworld in the best spirit of Alfred Nobel — for the greatest benefit to humankind.”