Physicists from the University of Konstanz have achieved a groundbreaking feat in generating some of the shortest signals ever produced by humans. These signals, with durations as short as five attoseconds (quintillionths of a second), offer unprecedented time resolution and open up new possibilities in studying ultrafast phenomena.
The researchers, Maxim Tsarev, Johannes Thurner, and Peter Baum, developed a method using femtosecond light flashes to generate electron pulses. By using pairs of femtosecond light flashes from a laser, the scientists were able to create extremely short electron pulses in a free-space beam. This breakthrough, reported in the journal Nature Physics, surpasses the time resolution of light waves and allows for the observation of ultrafast phenomena, including nuclear reactions.
To achieve such precise time resolution, the physicists utilized the concept of superimposing light waves to create standing or traveling wave crests and troughs. By carefully choosing the incidence angles and frequencies, the researchers made the co-propagating electrons overlap with the optical wave crests and troughs. The ponderomotive force then propelled the electrons in the direction of the next wave trough, generating a series of electron pulses that are exceptionally short in time.
The temporal duration of these electron pulses reached around five attoseconds, which the researchers examined by measuring the electrons’ velocity distribution after compression. They found that the distribution consisted of thousands of velocity steps due to the interaction of whole numbers of light particle pairs with the electrons simultaneously.
According to physicist Johannes Thurner, this temporal superposition of electrons with themselves, caused by the same acceleration at different times, has quantum mechanical implications for experiments involving the interaction of electrons and light.
In addition to the remarkable time resolution achieved, the researchers highlight the advantage of their experimental setup, which takes place in free space without the need for materials. This feature enables the use of lasers of any power for even stronger compression, potentially leading to the ability to observe nuclear reactions.
While the current research represents basic research in the field, Peter Baum, the head of the Light and Matter Group at the University of Konstanz, emphasizes the significant potential it holds for future studies. He envisions using the two-photon compression technique to trigger changes in materials and capture observations in a manner akin to a camera flash.
This groundbreaking achievement in generating ultrafast signals with attosecond durations not only expands our understanding of ultrafast phenomena but also opens up exciting possibilities for future research in various fields.