“Optical Tweezers” and Tools Used for Laser Eye Surgery Snag Physics Nobel

Optical physicists Arthur Ashkin, Gérard Mourou and Donna Strickland have won this year’s Nobel Prize in Physics for “groundbreaking inventions in the field of laser physics.”

Half of this year’s nine-million-kronor (about $1-million) prize goes to American physicist Arthur Ashkin for his invention of “optical tweezers,” lasers that can probe the machinery of life without causing damage. The other half will be split jointly between French physicist Gérard Mourou and Canadian physicist Donna Strickland for their development of “chirped pulse amplification” (CPA)—a method for making ultrashort, high-intensity laser pulses now routinely used in corrective eye surgery and precision machining. Strickland is the first female physics laureate in 55 years, and only the third in the prize’s long, venerable history. The new laureates will receive their prizes in December at a ceremony in Stockholm.

At 96, Ashkin is the oldest person to win a Nobel. His development of optical tweezers traces back to the 1960s, and culminated in 1986 during his tenure at Bell Laboratories in New Jersey. The technique uses the gentle pressure of light itself to trap and push a microscopic, transparent sphere into the center of a laser beam. The laser-controlled sphere can make and measure exceedingly minute forces when tethered to a biological sample, allowing researchers to delicately manipulate microbes, viruses and even a cell’s individual components. In a video played during a press conference at the Royal Swedish Academy of Sciences in Stockholm, Anders Irbäck, a physicist at Sweden’s Lund University and member of the Nobel Committee for Physics provided a simple demonstration of the principle behind Ashkin’s tweezers, using exhaust from a hair dryer to hold and manipulate a ping-pong ball in midair without touching it.

Mourou, 74, now a professor at the École Polytechnique in France, was Strickland’s academic advisor at the University of Rochester in New York State in the 1980s, where together they created CPA. Strickland, 59, is now an associate professor at the University of Waterloo in Ontario. Before their breakthrough, optical physicists had hit a wall in developing lasers of ever-increasing intensity. “The technology wasn’t scalable,” said Mats Larsson, a physicist at Sweden’s Stockholm University and member of the Nobel physics committee, speaking during the press conference. “It wasn’t possible to go to higher intensity because of amplifier damage.”

With CPA, Mourou and Strickland shattered this wall, sparking a trend that allowed lasers to, on average, double in intensity twice per decade. The technique relies on first stretching out short, energetic laser pulses in time, reducing their peak power and allowing them to be safely fed through an amplifier, after which they are finally compressed back to their original size—dramatically boosting their intensity. The resulting ultrabrief, ultrasharp beams can be used to make extremely precise cuts and holes in a variety of materials, and have been used in surgery to correct nearsightedness in millions of people.

“This year’s prize is about tools made from light,” said Göran Hansson, secretary general of the Royal Swedish Academy, summarizing awards during his remarks at the press conference. It was, to some degree, also about recognizing the achievements of women in the physical sciences.

Taking reporters’ questions via phone from her home in Waterloo, Strickland reacted with surprise when told only two women had preceded her in winning the prize: “Is that all, really?” she asked. “I thought there might have been more…. We need to celebrate women physicists because we’re out there, and hopefully in time it’ll start to move forward at a faster rate. I’m honored to be one of those women.”

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