10/02/2018 18:15:37

Nobel Prize in physics goes to 3 laser physics inventors

The 2018 Nobel Prize in physics has been jointly awarded to three people for their work in manipulating and cutting microscopic objects through laser physics.

What happened?

This year’s prize is split between three winners. Half goes to Arthur Ashkin from Bell Laboratories in Holmdel, U.S., who invented the “optical tweezers” — a method to trap atoms, nanoparticles, and viruses in between two beams of light.

The other half of the prize money is shared between Gérard Mourou from the University of Michigan and Donna Strickland from the University of Waterloo, Canada.

What did they do?

The optical tweezers created by Ashkin can manipulate living cells, such as viruses and bacteria, without damaging them.

Mourou and Strickland’s work resulted in “the shortest and most intense laser pulses created by humankind,” allowing for incredibly precise cutting or drilling through living matter. Their technique is called chirped pulse amplification, or CPA.

How did they do it?

In the 1970s, while attempting to exploit the radiation pressure of laser beams to push dielectric spheres, Ashkin discovered that another force nudged the objects toward the region of highest light intensity. The most intense part of any laser beam is in the middle, and the radiation pressure exerted by light onto the objects in its path pushes them toward the most intense part of the beam. The light is strongly focused and pushes the tiny particles toward the middle of the beam. This keeps them there, held steady, hence the name “optical tweezers.” The Nobel committee played a very jolly video with a hair dryer and pingpong ball to demonstrate the principle. You can watch it here.

Mourou and Strickland’s work led to the invention of a method for achieving the shortest, and most powerful, laser pulses ever made by humans. In 1985 the two published an article, which described a method to shorten the pulse of high-intensity lasers without damaging the material used to produce the light.

The laser pulses were slowed down, then they were amplified, and finally compressed into a shorter time. When the pulse is compressed in time and becomes shorter, more light is packed in the same tiny space. This means the intensity of the pulse increases greatly.

Why is it so important?

“The optical tweezer technique is actively used in biology — if you pick the wavelength so that the particle does not absorb the light, it does not heat up. Then you can move a living cell or organelles in a cell to the place that you need, and the cell does not die, it remains intact and viable. And it can be placed anywhere you need to within a few hundred nanometers, depending on the laser wavelength,” explains Dmitry Chubich from the Laboratory of 3D Printing Technologies for Functional Microstructures at MIPT.

Inspired by the 1985 Mourou and Strickland paper, scientists have steadily improved at generating ultrashort intense laser pulses, leading to advances in data storage, the measurement of phenomena on femtosecond and even attosecond timescales, and more. Today CPA is used around the world in a variety of applications, including corrective eye surgery.

What makes this Nobel prize unique?

Strickland is the third woman to get the Nobel Prize in physics, following Marie Curie in 1903 and Maria Goeppert-Mayer in 1963.

This year’s prize also sets another record, with Ashkin being the oldest person to win a Nobel prize, at 96 years of age. He began working on the laser technique in the ’60s, shortly after lasers were invented.

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