Rosa Weigand
Professor of the Department of Optics at the Faculty of Physical Sciences of the Complutense University of Madrid and Director of the Research Group "Laser Physics, Quantum Optics and Nonlinear Optics"
Once again, the Nobel Prize in Physics recognises excellent experimental work. On this occasion, recognition is given to work where the manipulation of light allows us to enter the world of electrons, where optics and atomic physics go hand in hand. In the late 1980s, lasers with ultra-short femtosecond pulses (1 fs=10-15 s) were sufficiently developed so that the start of the electromagnetic field could excite electrons bound at extremely high levels to a situation close to ionisation and that the end of the field would then bring the electron sharply closer to the nucleus. On this journey the electron releases energy in the form of highly energetic photons, in the form of coherent electromagnetic fields of very short wavelength. This is called high harmonic generation, HHG (High Harmonic Generation). Assembling these fields properly in time, the total field has a duration of attoseconds (1 as=10-18 s).
These are the fastest physical events that man can make, measure and use to follow the electronic dynamics in atoms and molecules. And if you can see what an electron does, its transition between orbitals in real time, it is clear that this is a new period for science. This is attoscience, one of the key disciplines of the 21st century.
This is basic science, but what are its applications? We have 80 years to go before the end of the century.