“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, 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.
Thinking outside of the box
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,” or CPA. 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 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.”
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.
But in a phone interview with the Swedish Academy, Strickland said her favorite application of high-power lasers is something she still demonstrates to undergraduate students in physics lab: white light generation. With this technique, a beam containing a narrow range of wavelengths is shot into a medium such as water, causing the waves to spread out into a rainbow. This is more advanced than Newton’s famous experiment with a prism; whereas he simply spread out light into its component colors, white light generation actually broadens the spectrum contained within a beam, creating the colored light.
“It’s a remarkable thing to see,” Strickland said, and it took decades for physicists to understand how it worked.
Strickland was a graduate student at the time of the CPA research; the 1985 article that announced the achievement was her first scientific publication.
The future of the prize
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.
Göran K. Hansson, secretary general of the academy, 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.”
