Traditionally, on the first Tuesday in October, the Nobel Committee announced the names of the winners of the Nobel Prize in Physics. The laureates of the prestigious award for the year 2023 are Pierre Agostini from Ohio University in the USA, Prof. Dr. Ferenc Krausz from the Max Planck Institute for Quantum Optics in Germany and Anne L’Huillier, a professor at Lund University in Sweden. As stated in the announcement, the prize was awarded to them for “experimental methods that generate attosecond pulses of light for the study of electron dynamics in materials.”
Namely, three scientists managed to create extremely short pulses of light that can be a new tool for the study of electrons, given that changes and processes in electrons take place unfathomably fast. “The generation of attosecond light pulses is made possible primarily by the development of modern and complex radiation sources such as free electron lasers and experimental setups for the generation of higher harmonics,” explains Dr. Aleksandar Krmpot from the Laboratory for Biophysics of the Institute of Physics Belgrade.
Changes in electrons occur in time intervals measured in attoseconds, and an attosecond is a billion billion times shorter than a second. The challenge is to produce such short pulses, and as Dr. Krmpot explains, the fundamental limitations of light pulses (even attosecond ones) are the central wavelength and the so-called spectrum width on which the pulses are generated. Namely, the pulse cannot be shorter than one radiation period.
“For a wavelength of 800 nm, which is close to the infrared region, we get a minimum pulse duration of about 2.5 fs (the typical wavelength of commercial fs lasers that have a pulse duration of about 100 fs, two such are used in our Biophysics Laboratory) while at a wavelength of 30 nm, the minimum possible duration of the pulse is 100 fs,” says Dr. Krmpot.
The vacuum technique is important in the generation of attosecond light pulses, and Dr. Krmpot explains that this is because the wavelengths are in the domain of vacuum UV radiation and soft H radiation.
Attosecond pulses of light can therefore be a good tool, and applications can be found in electronics, medicine and other fields. “They open the door to the study of fast processes in various fields of physics with a time resolution that is of the order of the duration of the pulse,” says Dr. Krmpot and adds that it is about very complex experiments that are mostly reduced to so-called pump-probe experiments. “One attosecond pulse and usually one fs pulse from a commercial laser in the near- infrared region arrive together at the sample. “By precisely controlling the delay of one pulse concerning another and repeatedly repeating the experiment in which the delay is gradually increased, it is possible to map a specific fast process in time,” explains Dr. Krmpot.