The Nobel Prize for physics in 2018 has been awarded to Arthur Ashkin, Gérard Mourou and Donna Strickland “for groundbreaking inventions in the field of laser physics”. Strickland is only the third woman to win the physics prize, and 55 years after the previous female winner (Maria Goeppert Mayer in 1963).
Ashkin is American, Mourou is French and Strickland is Canadian.
Their field of work is called laser optics.
Ashkin will take one half of the prize while Mourou and Strickland will share the other half.
Their specific citations read:
- Ashkin: “for the optical tweezers and their application to biological systems”
- Mourou and Strickland: “for their method of generating high-intensity ultra-short optical pulses”
In 1985, Steven Chu and his colleagues used lasers to trap atoms and cool them down to very low temperatures. As a result of this work, he won the Nobel Prize for physics in 1997. (He shared the prize with William Daniel Phillips and Claude Cohen-Tannoudji. Cohen-Tannoudji’s work, in turn, drew from the work of Shivaramakrishnan Pancharatnam, a little-known Indian physicist who worked on the optical techniques behind these methods in the first half of the 20th century.) After Chu’s win, Ashkin felt he had been unfairly left out because he had worked with Chu to perfect the technique. He has finally received his due, at least as far as the Nobel Prizes are concerned.
Ashkin’s achievement was to develop highly focused beams of laser that could exert forces on small objects like atoms and biological molecules and manipulate them, move them around – just the way we use chopsticks to eat some food items.
Strickland and Mourou invented a technique called chirped pulse amplification (CPA) in the 1980s. It is used to amplify the power of ultra-short lasers without damaging the medium that generates the laser, called the gain medium. CPA works as a two-step process, and is deceptively simple in its method. 1) An ultra-short laser pulse of low intensity is fired by a device, say an oscillator. 2) The first step of the CPA is to stretch out the laser pulse. 3) The stretched, low-intensity pulse is amplified into a stretched, high-intensity pulse. 4) The second step of the CPA is to compress the laser pulse. The complete process allows engineers to deliver an ultra-short, high-intensity laser pulse.
Optical tweezers and CPA have redefined how we use lasers today. Most high-intensity lasers around the world use CPA to deliver 1,000,000,000,000,000 watts of power in fractions of a second. This is more power than is generated in hundreds of large nuclear power plants combined. Scientists use such lasers to generate plasma-like states of matter and for ultra-precise cutting and machining.
Optical tweezers are, and have been, used to assemble cells to form intricate bio-networks, to manipulate atoms to undergo specific chemical reactions and to study how proteins interact with DNA.