Page 60 - EE Times Europe Magazine – November 2023

60 EE|Times EUROPE

THE INDUSTRY
Nobel Physicists Lay Attosecond Groundwork

for Quantum Discovery

By Stefano Lovati

he Royal Swedish Academy of instantaneous position of the hummingbird. atomic-scale research involving electronics,
Sciences awarded this year’s Nobel Now suppose we applied the same rea- in that it was not possible to generate pulses
Prize in Physics to three European soning to the atomic scale. To study and with durations shorter than this value using
T scientists who have made signifi- understand the dynamics of the extremely the available laser technology.
cant contributions to the field of attosecond rapid processes in which electrons take part, In the early 1980s, however, a significant
generation and measurement. Their research such as chemical reactions, it is necessary to discovery paved the way for the systematic
focuses on the experimental techniques used generate and measure the duration of vanish- generation of laser pulses with durations on
to produce attosecond light pulses, which ingly short pulses. the order of attoseconds. The key to gener-
have proved instrumental in investigating the At the molecular level, atoms move and ating attosecond pulses, researchers found,
intricate dynamics of electrons within various transform in timescales on the order of a lay in applying a combination of multiple and
forms of matter. femtosecond—a millionth of a billionth shorter wavelengths to produce them.
Researchers Pierre Agostini, Ferenc Krausz of a second, or 10 seconds. Advances in
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and Anne L’Huillier successfully demon- laser technology now allow molecular-level RESEARCH ON ATTOSECONDS
strated a methodology for generating highly phenomena to be studied by generating fem- In separate experiments over decades, this
compressed light pulses, which can be tosecond pulses. year’s Nobel Prize winners produced light bursts
effectively employed to gauge the swift phe- Compared with the nuclei of atoms, how- brief enough to capture individual frames of the
nomena associated with electron motion and ever, electrons are much lighter and move lightning-fast motion of electrons.
energy transitions. The ability to generate and much faster, and using femtosecond pulses The first results were obtained by L’Huillier,
measure light pulses of attosecond duration to study electron dynamics does not yield now a professor at Lund University (Sweden).
would make it possible to study and analyze a clear results. It is as if we were to photograph In experiments conducted in 1987, she dis-
number of quantum-mechanical processes. a hummingbird in flight with too long an covered that a noble gas hit by infrared laser
exposure time: The image of the wings would radiation emits radiation with a much higher
ATTOSECOND DEFINED be blurred, and it would be impossible to frequency, due to the presence of so-called
Suppose we wanted to use a determine its exact position. overtones. These overtones are high-order
continuous-shooting camera to capture an Electrons change position at speeds of up harmonics with frequencies that are multiple
event that occurs in a fraction of a second, to a few hundred attoseconds. One attosecond of the laser frequency. In the 1990s, L’Huillier
such as the beating of a hummingbird’s equals a billionth of a billionth of a second and others proposed an explanation for the
wings. Capturing the dynamics of this event (10 seconds). There are as many attoseconds experimentally observed phenomenon: The
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by obtaining a sequence of sharp, blur-free in a second as the number of seconds that have radiation emitted at high frequency is due to
images would require a high frame rate— elapsed since the Big Bang, which took place processes involving individual electrons.
for example, 30 to 50 fps. The shorter the some 13.8 billion years ago (Figure 1). When an electron is hit by the laser pulses,
exposure time, the greater the probability For a long time, the femtosecond was it acquires enough ionizing energy to allow it
of obtaining a sharp image with the exact regarded as an insurmountable limit on to temporarily leave its atom via the tunnel-

ATTOSECOND HEARTBEAT AGE OF THE UNIVERSE
1/1,000,000,000,000,000,000 1 SECOND 1,000,000,000,000,000,000
SECOND SECONDS
Electrons’ movements in atoms and molecules are so rapid that they
are measured in attoseconds. An attosecond is to one second as one
second is to the age of the universe.

©Johan Jarnestad/The Royal Swedish Academy of Sciences

Figure 1: In one second (the “heartbeat” period), there are 10 attoseconds, more than the number of seconds that have elapsed since
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the Big Bang. (Source: Johan Jarnestad/Royal Swedish Academy of Sciences ) 1
NOVEMBER 2023 | www.eetimes.eu