Researchers Develop Plasma Lens to Enhance Attosecond Pulses

A team of researchers from the Max Born Institute in Berlin and DESY in Hamburg has made a significant advancement in the field of ultrafast optics by developing a plasma lens capable of focusing attosecond pulses. This innovative technology, detailed in a recent publication in Nature Photonics, enhances the power of attosecond pulses, paving the way for new experiments that explore ultrafast electron dynamics.

Attosecond pulses are incredibly brief bursts of light, lasting only a few billionths of a billionth of a second. They are essential for observing and manipulating electronic motion in various materials, including atoms, molecules, and solids. Traditionally, focusing these pulses, which fall within the extreme-ultraviolet (XUV) or X-ray regions of the electromagnetic spectrum, has posed significant challenges due to the inadequacy of conventional optics. Standard mirrors tend to exhibit low reflectivity and degrade quickly, while lenses designed for visible light absorb XUV radiation, thereby distorting the attosecond pulses.

To overcome these limitations, the researchers created a plasma lens by sending strong electrical pulses through hydrogen gas contained in a small tube. This process strips electrons from hydrogen atoms, forming a plasma. The electrons then migrate outward, shaping the plasma into a concave lens. Unlike typical lenses that disperse light, the unique properties of plasma allow it to focus attosecond pulses effectively.

The study demonstrates that the plasma lens can focus attosecond pulses across various ranges of XUV light, with a tunable focal length that can be adjusted by varying the plasma density. The researchers achieved an impressive transmission rate of over 80%, significantly improving the efficiency of the focusing process. Notably, the plasma lens also acts as a filter for infrared driving pulses, eliminating the need for conventional thin metal filters and enabling more attosecond power to pass through.

With this enhanced capability, scientists can conduct attosecond experiments that were previously constrained by limited light sources. The research team employed computer simulations to analyze the temporal behavior of the focused pulses, observing that the pulse duration stretched only slightly, from 90 to 96 attoseconds. In real-world conditions, where different colors of the attosecond pulse may arrive at different times—a phenomenon known as chirp—the plasma lens was found to actually shorten the pulse duration from 189 to 165 attoseconds.

By successfully demonstrating a plasma lens for attosecond pulses, the researchers have addressed a crucial barrier in the field of attosecond science. This technique offers several advantages, including straightforward alignment, high transmission, and the ability to focus light across a range of wavelengths. These innovations open new avenues for applications that include mapping electron dynamics in complex materials, advancing quantum technologies, and enabling the next generation of ultrafast microscopy.

The implications of this development are vast, potentially transforming how researchers study and manipulate ultrafast phenomena. As scientists continue to explore the frontiers of attosecond science, the plasma lens represents a significant leap forward in our understanding of electron dynamics and their applications.

For further details, refer to the study by Evaldas Svirplys and colleagues, titled “Plasma lens for focusing attosecond pulses,” published in Nature Photonics on November 5, 2025. DOI: 10.1038/s41566-025-01794-y.