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: Researchers from the MPIK in Heidelberg used an atomic gas as a time-dependent lens to shape and spectrally manipulate intense high-frequency laser pulses. This gas-based optical element could pave the way toward better XUV- and X-ray pulse control for applications such as chemical reaction steering, quantum computing, and advanced spectroscopy methods for fundamental science.
The paper is published in the journal Science Advances. One of the first known human-made lenses to manipulate light dates to 700 B.C.: A nearly 4-centimeter-wide (1.6 inches) piece of rock crystal, manufactured around that time, was found in Nimrud, Iraq. Although the lens' original intended function is not entirely clear today, it shows that humans were aware of the light-focusing properties of materials even then.
An important application of this knowledge was the invention of microscopes more than two millennia later, which used the optical properties of focusing glass lenses to explore the previously unknown microscopic world. With the invention of lasers and later short, intense laser pulses, scientists can now produce high-energy light at extreme intensities for very short periods, enabling more precise material processing options and opening up further insights into microscopic processes. The shorter the wavelength of the light used, the shorter the pulses can be—and the more precisely we can peer into the quantum world of atoms and molecules.
In the extreme ultraviolet (XUV) spectral range, which spans wavelengths from a few to several tens of nanometers, this enables pulse durations in the attosecond range (1 attosecond = 10⁻¹⁸ seconds)—fast enough to directly track the movement of electrons. With the rapid development of large-scale free-electron laser (FEL) facilities, scientists can now generate ultrashort, high-brilliance XUV light pulses. However, versatile tools to shape and manipulate these beams remain scarce.
While conventional optical elements, mostly made of glass, such as lenses, mirrors or prisms, easily bend, focus or spectrally split visible light, high-energy XUV photons are strongly absorbed by such standard optical components rather than reflected or refracted. But controlling the shape and spectral composition of these short-wavelength pulses is of great interest in modern physics, as many atomic transitions are found within this energy range, and specifically addressing them could open up new pathways, for example, in controlling chemical reactions or developing ultrafast atomic-scale quantum computers. An international collaboration led by researchers from the Max-Planck-Institut für Kernphysik in Heidelberg (MPIK) has demonstrated the shaping of an XUV laser pulse both spatially and in its spectral composition.
They took advantage of the complex nonlinear interaction between intense light and matter. When an intense XUV laser pulse passes through an optically dense medium—such as an atomic gas—it quickly excites and de-excites the atoms' energy levels. This dynamic quantum process is known as Rabi oscillation, rapidly transferring electrons between those quantum levels.
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