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‘Optical Tweezers’ awarded with Nobel Prize in Physics

October 10th, 2018 | by Theo Turvill
‘Optical Tweezers’ awarded with Nobel Prize in Physics
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Laser technology was announced as the 2018 Nobel Prize in Physics theme on 2 October, with the award being handed to a trio of physicists: Dr Arthur Ashkin, for his work on creating the ‘laser tweezers’ and Drs Strickland and Mourou for their contributions in increasing the optimal intensity of the lasers.

Dr Ashkin’s contribution runs counter to the familiar idea seen in sci-fi of the tractor beams often adopted by many an alien to levitate things into their crafts for ‘probing’. Rather than pulling towards, Dr Ashkin’s invention employed tiny laser beams to push away objects.

Dr Donna Strickland and Dr Gerard Mourou received the Nobel Prize for their work on boosting the maximum power of lasers.

The science behind the invention is somewhat similar to the classic physics class demonstration of a ping-pong ball levitated in the warm air-current of a hair dryer. Instead of air, laser light is used. Dr Ashkin’s invention applied the theoretical work of Maxwell in 1862 which was later observed by Lebedev in 1990, that light bringing photons carry momentum. Through refinements, Dr Ashkin was able to hold stationary minuscule objects down to the size of individual atoms, manipulating them through three dimensions in a stream of laser light. His invention has been used in the probing of minute biological machines as well as in the atom by atom assembly of new chemical compounds.

Dr Donna Strickland and Dr Gerard Mourou received the Nobel Prize for their work on boosting the maximum power of lasers.

Throughout the 60’s laser power quickly increased, stalling a few years prior to the 70’s, flat-lining well into the mid 80’s due to the physical components of lasers not being able to withstand the intensity of high-powered beams. Dr Strickland’s work as a PhD student with Dr Mourou as her supervisor on the idea that became known as Chirped Pulse Amplification, was able to negate this issue.

The technicalities of the process are complex, though the idea is graspable. A laser initially starts as a high-powered short duration blast. The laser is then stretched out, lasting longer and reducing the intensity of the ray, minimising damage to the components within the device. At the optimal moment, the ray is transferred back from an elongated beam to its initial short duration high intensity blast.

As a result of this newfound technique, modern lasers can house a high-power blast possible of generating one-million times the power of a nuclear reactor. Procedures such as laser eye surgery would be impossible without this advancement.

 

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