Nobel Prize in Physics 2018: Tools made of light, Optical tweezers and High-power laser pulses

Nobel prize winners in physics 2018, From left: Donna Strickland, Gerard Mourou  and Arthur Ashkin

Nobel Prize in Physics 2018: Tools made of light, ‘optical tweezers and high-power laser pulses

The Nobel Prize 2018  in Physics was awarded to three scientists (Arthur Ashkin from the United States of America, Gerard Mourou from France and Donna Strickland from Canada), for creating “Optical Tweezers. Tools made of Light, and high power laser pulses". Three of the winners won the award for groundbreaking inventions in the field of laser physics. In this process, 59-year-old Canadian scientist Strickland has now become the third woman to receive the Nobel Prize in Physics after Marie Curie and Maria Goeppert in 1903. 

2018 Nobel prize winners in physics

Arthur Ashkin:

Arthur Ashkin has received the prize for the optical tweezers and their application to biological cells.  Ashkin's optical tweezers are capable of catching particles, atoms, viruses and other living cells along with their laser beam fingers, allowing the American researcher to realize 'an old dream of science fiction' using the radiation pressure of light to move physical objects. Science fiction has become a reality.  Optical tweezers make it possible to observe, turn, cut, push and pull with light. In fact, a physical instrument rather than a technology, these "tweezers" are widely used for the detection of different and very small particles, such as individual atoms, biological cells or DNA strands.

The tweezers can capture living bacteria without harming them, a breakthrough he achieved back in 1987. Since then, these instruments are widely used to check the machinery of life. In fact, many scientists have been awarded the Nobel Prize since then when they worked on the developed technology, but so far Ashkin himself had been left out.

Ashkin has worked on laser pulses ever since they were first produced in 1960. Light beams produced by a laser — it is a device and not a beam itself — have a single frequency (color) and high intensity, and thereby high power. It was widely known for many years that light could put pressure on those things on which this incident occurred. But this pressure was not so great that there would be any effective impact assessment of scientists. Due to the development of laser beams, due to their high power, new opportunities opened. For the first time, Ashkin showed that these light beams can actually be used to move very small objects. He found that the micrometer-sized spheres he had been using for his experiments were drawn towards the center of the light beam, where the intensity of the light, or the number of light particles in the beam, was the most.

Gérard Mourou and Donna Strickland:

They have been jointly awarded the other half of the Prize for their method of generating high-intensity, ultra-short optical pulses. They developed a technique that has made it possible to generate most intense laser pulses without destroying the amplifying material, that is now used in a wide variety of scientific and medical applications, including in eye surgeries. Mourou and Strickland devised a way out. They increased the duration of the pulses before amplifying the light so that the intensity decreases. The light could then be amplified normally. After amplification, the pulse could be compressed back to its original time duration, packing many more light particles in a very small space, thereby increasing the intensity by the different order of magnitude. Through this method, Morou and Strickland can improve the intensity of the light beam approximately one million times at a time. Scientists have since developed this technology further so that modern-day laser can produce light beams with the power of the order of petawatts, and efforts are on to install lasers that can go even higher.

Chirped-pulse amplification

The technique for generating high-intensity, ultra-short optical pulses developed by Professor Mourou and Dr. Strickland has enabled scientific discoveries in a number of fields and provided the basis for important scientific approaches used in Swinburne's research.

Chirped-Pulse Amplification (CPA) allows high-energy pulses to be produced every microsecond – a million pulses per second – which means that spectroscopy measurements can be performed in a reasonable time, allowing sufficient data to be acquired to minimize noise levels on weak signals. This also makes it possible to change different control parameters to build up a comprehensive picture of the important factors affecting the dynamics and mechanisms of the specific process of interest. Along with testing novels and complex materials, these high-energy, ultrasound laser pulses can also be used to control the properties of these materials, and even drive them to change the state, which becomes the novel quantum state of substances.

Associate Professor Jeff Davis explained "These extremely short-duration pulses are necessary to measure the evolution of sub-atomic particles such as electrons. The field of study is ultrafast 'femtosecond' spectroscopy. A femtosecond is one billionth of a second. If we want to measure how fast something is moving, we need a starter's gun to set things going and something to stop the clock. But when we want to measure the precise evolution of electrons, which can change their properties or their state in femtoseconds, we need to be able to start and stop the clock much, much faster. We use femtosecond laser pulses to achieve this. Ultrafast laser pulses allow exquisite control over the properties of the material, giving us the potential for ultrafast switching. This exquisite control and our ultrafast measurement of dynamics will allow us to fully understand these phase transitions, allowing us to optimize their control in future devices. So, it is fundamental science, but with an immediate application.