The Nobel Prize in Physics 2018 was awarded “for groundbreaking
inventions in the field of laser physics" with one half to Arthur Ashkin “for the
optical tweezers and their application to biological systems", the other half
jointly to Gérard Mourou and Donna Strickland “for their method of generating
high-intensity, ultra-short optical pulses.”
Optical Tweezers, developed by Arthur Ashkin in 1987 use the radiation pressure of
laser light to confine a microparticle , such as a virus, in three dimensions
without any damage. It uses the "gradient force", proportional to the gradient of
the intensity of the laser beam, to generate the three-dimensional potential well.
This cannot only sense dynamics of microparticles but also apply controlled forces
and torques without a physical touch.
Femtosecond laser pulses at high intensities have enabled controlled access to
physical phenomena in the femto-, atto- and even zepto-second timescales. The
femtosecond pulses enable extreme UV (EUV) light sources for lithography and fast
ions for therapy. To generate high intensity short laser pulses, Strickland and
Mourou invented a technique known as chirped pulse amplification (CPA). In order
not to destroy the amplifying medium they stretched the laser pulses in time to
reduce their peak power before amplifying them. Amplified pulses were then
compressed in time to become shorter with extremely high peak powers. CPA’s uses
include the millions of corrective eye surgeries that are conducted every year
using the sharpest of laser beams.
The speakers will explain the physics and applications of these techniques to a
general audience.