This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: By superimposing two ultrashort laser pulses that converge from different directions, a team of physicists at the University of Oldenburg has succeeded in generating three-dimensional light fields. Using the same method, they were also able to excite electrons into quantum states that had previously been inaccessible in experiments.
This approach opens up new experimental avenues for identifying chiral structures, controlling interactions between light and matter and generating specific electronic quantum states, the researchers report in the journal Physical Review Research. "With our method, we can generate electronic quantum states that have previously only been described theoretically and also make them spatially visible," explains Dr. Matthias Wollenhaupt, who leads the research team.
"We have thus expanded the experimental optics toolkit to include a new class of three-dimensional light fields." To generate the 3D light fields, the team superimposed two specially shaped femtosecond laser pulses. These are extremely short bursts of light that last just a few millionths of a billionth of a second. The researchers combined two laser beams of different colors, making the beams intersect at a single point and thus creating three-dimensional light fields whose shape they were able to control.
"The fields oscillate in all three spatial directions, opening up new possibilities for investigating and controlling specific light-matter interactions," explains Darius Köhnke, one of the two lead authors of the study and a Ph.D. student in the Ultrafast Coherent Dynamics research group. The key advantage of this procedure is that researchers can use 3D light fields to generate quantum states of electrons that were previously inaccessible in experiments. The team demonstrated this by using their 3D light field to selectively excite electrons in potassium atoms into higher-energy states—known as excited states—and then release them from the atoms.
The researchers were able to simultaneously observe the changes in the electron states at short intervals. Their method thus functioned like an ultrahigh-speed camera for quantum processes: As with the stroboscopic flash lighting technique, they were able to capture the successive stages of the different electron states, forming a movie of their evolution. The researchers explain that the new method is particularly promising for the investigation of chiral molecules, which play a key role in biology and medicine.
Chiral molecules exist in two forms that are mirror images of each other but cannot be superimposed, much like a pair of human left and right hands. Many biomolecules, including amino acids, carbohydrates and active ingredients in medicinal products, can be chiral. Their two forms frequently have different properties.
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