The Nobel Prize in Physics 2018 - " The Optical Tweezers and High-Intensity Ultra-Short Pulses "

November 09, 2018

The Nobel Prize in Physics 2018 - " The Optical Tweezers and High-Intensity Ultra-Short Pulses "

Alfred Nobel

Nobel Prize was created by the will of Alfred Nobel, a notable Swedish Chemist, Engineer and Inventor. The will of the Swedish Scientist Alfred Nobel established five Nobel Prizes in 1895 which were first awarded in 1901 in Chemistry, Physics, Peace, Literature and Physiology or Medicine. This set of annual international award is presented in several categories by Swedish and Norwegian institutions in recognition of academic, cultural, or scientific advances for the greatest benefit to Humankind. Further, in 1968 Sweden's Central Bank established Sveriges Riksbank prize in Economic Sciences in memory of Alfred Nobel, which although not being as a Nobel prize is informally known as the - " The Nobel Prize in Economics ". Many of us wonder that why there isn't any sort of Nobel Prize in Mathematics, well one of the most common and un-founded reasons as to why Alfred decided against a Nobel Prize in Mathematics is that a woman he proposed [rejected him because of/cheated him with] a famous Mathematician. Following Swedish and Norwegian Institutes decides the candidates/organisation to be awarded Nobel annually.

Alfred Nobel will states that 94% of his assets will be used to establish Nobel Prizes

Nobel Prize in Physics :- Royal Swedish Academy of Sciences
Noble Prize in Economic Sciences :- Royal Swedish Academy of Sciences
Nobel Prize in Chemistry :- Royal Swedish Academy of Sciences
Nobel Prize in Medicine :- Nobel Assembly at the Karolinska Institute
Nobel Peace Prize :- Norwegian Nobel Committee
Nobel Prize in Literature :- Swedish Academy

The Prize ceremony takes place annually in Stockholm, Sweden (with the exception of the Nobel Peace Prize ceremony, which was held in Oslo, Norway). The Prize ceremony is held on 10th December annually in the memory of Alfred Nobel and 10th December is also known as Nobel Prize Day. This prize is not awarded posthumously (after the death of the originator). However, if a person is awarded a prize and dies before receiving it, the prize may still be presented. A prize may not be shared among more than three individuals, although the Peace Prize can be awarded to an organisation of more than three people

The Nobel Committee's Physics Prize shortlist cited Wilhelm Rontgen's discovery of X-Rays and Philipp Lenard's work on Cathode Rays. Further, Wilhelm Rontgen received the first Nobel in Physics for his discovery of X-Rays.

Nobel Prize in Physics 2018

Noble Prize in Physics 2018

This year the Nobel Prize in Physics is awarded to three candidates, with one half awarded to Arthur Ashkin for the optical tweezers and the other half jointly to Gerard Mourou and Donna Strickland for their method of generating high-intensity, ultra-short optical pulses.

The Curies are the most successful, when it comes to number of awarded Nobel Prizes in a family among - The Bragg's and The Einstein's. Between 1901 and 2018, the Nobel Prizes were awarded 590 times to 935 individuals/organisations and among them, 52 women have been awarded the Nobel Prizes.

Arthur Ashkin - " The Optical Tweezers "

Arthur Ashkin is the oldest person ever to win a Nobel Prize at the age of 96. He was born on 2 September 1922 and he is known as the father of the Optical Tweezers. Arthur and his colleagues invented the Optical Tweezers in 1986 which is used as an Optical Trapping instrument at a microscopic level. He did his work and research at Bell Laboratories and Lucent Technologies and currently resides in New Jersey.

The Optical Tweezer's

Optical Tweezers is an instrument via which light can hold things up at a microscopic level and it acts as a very sensitive way of measuring, that when things are being pulled or pushed for example and it's a really clever piece of Physics used to do that.

So, Ashkin took a laser beam and a very small glass of plastic sphere that is not much larger than the wavelength of light and he placed it in the laser beam and it turns out that a little plastic sphere will stay in the laser beam when he placed it right there.

Experimental Setup

So, here's an laser beam which is brighter in the middle i.e more intense in the middle and gets fainter when we move outwards and here the dotted line shows the mid-line. So, when the laser lights interact with this little transparent sphere, it goes through it and then gets refracted like we all have studied in the case of rainbow and it happens because the little sphere has an different refractive index than the laser beam. In result, the light bend towards upward and on the other side the light bend towards downward but because the light was more intense at the middle, more of the light gets bend towards upward and light also carries momentum. So, the momentum of the light bend towards upward is more than the momentum of the light bend towards downward. So, the net momentum is towards upwards but, momentum needs to be conserved. In order to do so, the little sphere starts to move back and forth in order to conserve momentum and further it starts to behave like an spring balance and further Ashkin used this optical tweezer as an spring balance in order to measure forces at very small scales (at microscopic level). So in order to do so we Ashkin glued some molecules (like DNA) at the little sphere to measure the displacements and the forces.

DNA glued at the top of the sphere to measure displacement at microscopic level

As we know that light carries momentum, so some of the light gets refracted while some of the light gets absorbed by the little sphere that means that there's an transfer of momentum which makes sphere to move forward along with the beam but Ashkin wanted to make that sphere stable at a specific position to make the experiment work out. So Ashkin wanted somehow to stop the sphere to move along with the beam and he wanted to make it stable.

To remove this problem Ashkin firstly tried to place the experiment vertically up instead of placing it horizontally down in order to stop the little sphere to move because when he placed the experiment vertically up then gravity opposed the little sphere to move upward and then Ashkin was able to make the sphere stable by introducing few variations in the intensity of the laser beam. But, this doesn't worked particularly well to determine the required specific calculations.

The new method introduced by Ashkin to make the experiment more accurate

Further, Ashkin introduced a much settled way to drive the experiment more accurately. Instead of having light as a parallel beam, he placed an strong lens before the little sphere so that light falls as an convergent beam on the sphere and then light still gets refracted but, the light going outward was travelling much more than the light coming inward. So, the light going outward was having more momentum than the light coming inward because the light which was coming inward was travelling a very small distance. So, the net transfer of the momentum pushes the sphere backwards. In result the motion experienced by the sphere was balanced by the conversation of momentum which further made the sphere to stay at a particular position i.e it made the sphere much more stable.

Optical Tweezers are known for their applications in Biology. Recently many researcher's have used Optical Tweezers to check the validation of Newton's Law of Gravity at very small scale. These tweezers are so incredibly sensitive that they can even measure the gravitational effects at such scales and this is the first time when researcher's around the globe are studying gravity at such a tiny scale.