Scientists Create First Attosecond Atomic X-Ray Laser
By SLAC National Accelerator Laboratory
A one-quintillionth-of-a-second lasing breakthrough could lead to next-generation X-ray technologies, improving imaging in medical, materials, and quantum science.
Scientists at the University of Wisconsin-Madison, the U.S. Department of Energy’s SLAC National Accelerator Laboratory, and others have created the first attosecond atomic X-ray laser.
In a new study published in the journal Nature, the researchers describe how they focused a short, powerful X-ray input pulse – with power equivalent to focusing all the sunlight that hits the Earth into a one square millimeter target – onto copper and manganese targets. Depending on how the laser was configured, some of the resulting X-ray laser pulses lasted less than 100 attoseconds, or billionths of a billionth of a second.
Perhaps as significant, this new X-ray laser operates more like a conventional laser than other existing X-ray lasers, potentially opening the door to applications studying the fastest processes in nature. The results hold promise for quantum computing, atomic clocks, and developing laser technology to study medical and materials science at the atomic level, the researchers say.
“Considering over six decades in laser development and tremendous challenges in translating many of the concepts to X-ray wavelengths, the realization of an attosecond atomic X-ray laser is a major leap forward in laser and quantum science,” said Matthias Kling, Science and R&D Division director at SLAC’s Linac Coherent Light Source(LCLS), the world’s most powerful X-ray free-electron laser (XFEL). “Free-electron lasers were crucial in creating the extreme conditions to make this possible.”
How An Attosecond Atomic X-Ray Laser Is Made
The team used high-energy pulses from LCLS and Japan’s SACLA XFEL to create this laser through stimulated emission. In this study, the pulses were focused onto copper or manganese targets, with the XFEL’s energy tuned high enough to excite those metals’ tightly held innermost electrons. An initial pulse excited the atoms’ inner-shell electrons, emitting X-ray light as they returned to their ground state. These photons sometimes hit an already-excited atom, leading to an avalanche of what’s called stimulated emission in one direction. That X-ray light from this chain reaction in the target emits in the same direction as the initial pulse.
3 Unique Laser Properties
“We observed a strong lasing phenomenon in inner-shell X-ray lasing, simulating and calculating how it evolves,” said Uwe Bergmann, physics professor at UW-Madison, visiting faculty at SLAC and senior author on the study. “When you calculate the X-ray pulses that come out, they are incredibly short – shorter than 100 attoseconds.”
Making an X-ray laser in this way has significant advantages. XFEL pulses are generally irregular, with each pulse really being made of several short, intense spikes. In contrast, an atomic X-ray laser forms clean, controlled pulses similar to those of a traditional laser.
The lasing in the copper and manganese samples also underwent Rabi cycling, where the pulse is so strong that the atom will absorb light and re-emit that light back out, generating extremely short X-ray pulses. In addition to shortening the X-ray pulses, demonstrating Rabi cycling is the first step to the development of many modern laser techniques that are currently used with optical lasers in various industrial applications from quantum computing to telecommunications.
Why This Matters
This breakthrough, creating an atomic X-ray laser with sub-100 attosecond pulses, allows researchers to study how electrons move inside atoms with unprecedented precision. These advances could lead to next-generation X-ray technologies, improving imaging in medical, materials, and quantum science.
“Development of such pulses allows us to use traditional laser techniques with X-rays to study electron motion in molecules and materials on their natural length and timescales,” said Thomas Linker, lead author and joint postdoctoral researcher at UW–Madison and SLAC.
Bergmann said the results are significant for the laser community. “There are so many technologies and phenomena that the laser community uses now, but very few of those have dared to have been tried with hard X-rays,” Bergmann said. “Hard X-rays are very powerful: They have short wavelengths that provide atomic spatial resolution, and they are sensitive to different atomic elements. This work is a step toward pushing the exciting field of real laser science into this powerful hard X-ray regime.”
This research was funded by the DOE Office of Science, the NIH, and the Ruth L. Kirschstein National Research Service Award. LCLS is a DOE Office of Science user facility. Computer resources for simulations were provided by the National Energy Research Scientific Computing Center, a DOE Office of Science user facility.
About SLAC
SLAC National Accelerator Laboratory explores how the universe works at the biggest, smallest, and fastest scales and invents powerful tools used by researchers around the globe. As world leaders in ultrafast science and bold explorers of the physics of the universe, we forge new ground in understanding our origins and building a healthier and more sustainable future.
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SLAC is operated by Stanford University for the U.S. Department of Energy’s Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time.