Attoseconds, the billionths of a billionth of a second, are the shortest flashes of light ever created. Now, scientists have figured out how to focus them.<\/p>\n
A team from the Max Born Institute (MBI) in Berlin and DESY in Hamburg has built the world\u2019s first plasma lens capable of focusing attosecond pulses, a feat that could transform ultrafast physics.<\/p>\n
The breakthrough dramatically boosts the power of attosecond light used to probe the fastest electron motions in atoms and materials.<\/p>\n
Attosecond pulses are used to freeze and film electrons in motion, offering a window into the most fundamental processes of matter.<\/p>\n
But there\u2019s been one stubborn problem: these pulses fall in the extreme-ultraviolet (XUV) or X-ray range, where conventional mirrors and lenses fail.<\/p>\n
Mirrors have poor reflectivity and degrade fast, while normal lenses absorb XUV light and stretch the attosecond pulses, blurring their precision.<\/p>\n
That\u2019s why researchers at MBI and DESY turned to an unconventional material: plasma, a charged gas that can bend light in ways solids cannot.<\/p>\n
By creating plasma in a controlled way, the team produced a new kind of lens capable of focusing attosecond light without losing its power or speed.<\/p>\n
Plasma bends the rules<\/p>\n
To build the lens, scientists sent strong electrical pulses through hydrogen gas inside a narrow capillary tube. The pulses stripped electrons from hydrogen atoms, forming a plasma. As the electrons pushed outward toward the tube walls, the plasma shaped itself like a concave lens.<\/p>\n
\u201cNormally, such a lens would spread light out rather than focus it,\u201d the team explained. \u201cBut because plasma bends light differently than ordinary materials, it instead focuses the attosecond pulses.\u201d<\/p>\n
In their experiments, the researchers showed that the plasma lens could focus light across a wide range of XUV wavelengths, with its focal length adjustable by tuning the plasma density.<\/p>\n
Even more impressive is that it achieved a transmission rate above 80 percent, meaning most of the light passed through intact.<\/p>\n
More power, fewer filters<\/p>\n
The plasma lens also acted as a natural filter, blocking the longer infrared laser pulses that usually drive attosecond generation.<\/p>\n
These infrared pulses typically require additional metal filters, which eat up valuable energy.<\/p>\n
\u201cThis means those filters are no longer necessary,\u201d the team said. The result: more attosecond power for experiments that are often limited by weak light sources.<\/p>\n
To understand the lens\u2019s effect on pulse shape, scientists ran simulations. The attosecond pulses stretched only slightly from 90 to 96 attoseconds.<\/p>\n
In realistic conditions, where the pulse colors arrive at slightly different times (a phenomenon known as chirp), the plasma lens even shortened the pulses<\/a> from 189 to 165 attoseconds.<\/p>\n With simple alignment, tunable focusing, and high transmission, this plasma lens could usher in a new era of attosecond science, from mapping electron motion in complex materials to advancing ultrafast quantum<\/a> technologies and microscopy.<\/p>\n