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The pulses of light that open a door to the microcosm

“At the time, I couldn’t imagine that my experiment could create such short pulses of light,” Anne L’Huillier later said of the discovery that paved the way for the Nobel Prize. Photo: ERCEA.
“At the time, I couldn’t imagine that my experiment could create such short pulses of light,” Anne L’Huillier later said of the discovery that paved the way for the Nobel Prize. Photo: ERCEA.

This is the science behind the unimaginably quick attosecond pulses. The method can “photograph” electrons, giving us new insights into the inner life of atoms, and is the discovery that earned Anne L’Huillier this year’s Nobel Prize in Physics.

Electrons move so unbelievably fast that they were long thought to be unobservable. Yet despite the difficulties, many researchers were determined to try in various ways. But why? Out of sheer curiosity, of course.

And also, because the knowledge could translate into practical benefits. If we learn more about nature’s smallest building blocks, we can eventually control them. Since electrons control the properties of all materials – electrons are the atom’s contact surface with the outside world – there is potential for their application in virtually all areas in which the aim is to influence materials at the molecular and atomic levels.

Future areas of application

Perhaps the laser method that creates these attosecond pulses might allow us in the future to better understand photosynthesis and create more efficient solar cell technologies. Or build electronics at the molecular level. Several medical applications have also been mentioned. Some tracks are already being worked on today while others are still at the idea – or dream – stage.

Back to the basic research. It is impossible to “see” an electron cloud in real-time, but thanks to attosecond pulses, electrons can be studied by the indirect imaging of some of their properties.

From pulse to picture: a method in seven steps

An electron bouncing around in a laser field, captured by attosecond pulses.
An electron bouncing around in a laser field, captured by attosecond pulses.

Attoseconds and lasers

An attosecond is a billionth of a billionth of a second, which is so short that there are as many of them in a second as there have been seconds in the entire history of the universe.

Invented in the 1960s, lasers differ from ordinary light in two ways: Firstly, all the light waves move in tandem and not in a jumbled fashion as is the case in normal light. Secondly, the light moves in the same direction and is not scattered like other types of light. The benefits are that the light produced is extremely intense and controllable. Today, lasers are used in industry, healthcare and in some everyday gadgets. The lasers used by Anne L’Huillier and her colleagues are much more powerful.