Some processes in physics happen in the blink of an eye, while others happen in the blink of a photon. This year’s Nobel Prize in Physics was awarded to Pierre Agostini of the Ohio State University, Ferenc Krausz of the Max Planck Institute of Quantum Optics in Garching, Germany, and Anne L’Huillier of Lund University in Sweden for developing the field of ultrafast laser pulses. L’Huillier is only the fifth woman to have ever won the Nobel Prize in Physics.
These pulses are on the scale of the attosecond—a billionth of a billionth of a second. This duration is so short that there are as many attoseconds in a single second as there have been seconds in the entire history of the universe. This year’s prize was awarded “for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter.”
“Attosecond science allows us to address fundamental questions,” said Eva Olsson, chair of the Nobel Committee for Physics, at a press conference today. At the atomic level, the motions of electrons and nuclei typically take place over the course of attoseconds. In the late 19th century early photographers made use of cameras to determine whether a horse took all of its hooves off the ground at a gallop—a process too fast for the human eye to discern. (Spoiler: horses do completely leave the ground.) Today’s researchers hope to do the equivalent at attosecond timescales by using ultrafast lasers to get clearer views of otherwise blurry atomic processes.
But generating light in extremely short pulses is not easy. For many years light pulses were stuck in the femtosecond regime (one femtosecond is 1,000 attoseconds). That’s good enough to resolve molecules in chemical reactions, a feat that won the 1999 Nobel Prize in Chemistry—but it’s insufficient to spot the zigging and zagging of speedier electrons.
L’Huillier broke down some of the first barriers in 1987, when she discovered that passing an infrared laser through a noble gas, such as argon, led to a pattern in the emitted light: a plateau in the frequency. This plateau would prove vital for work done in the early 2000s, when Agostini created multiple 250-attosecond-long pulses of light while Krausz, working independently, generated single 650-attosecond-long pulses.
With the newfound probes developed by Agostini, Krausz and L’Huillier, researchers can now generate laser pulses of merely a few dozen attoseconds. Further refinements of these techniques to generate ever shorter pulses promise to deepen scientists’ understanding of electron dynamics and could lead to breakthroughs in medical diagnostics, as well as the development of novel semiconductors.
As usual, the award came as a surprise to its recipients. When L’Huillier was notified, she was in the middle of giving a lecture and missed the first few calls from Stockholm. After stepping outside to take the call, she returned to the lecture where she continued teaching without telling her students anything. “Teaching is very, very important. For me, it’s very important,” she told Hans Ellegren, secretary-general of the Royal Swedish Academy of Sciences, over the phone during the prize’s announcement.
