CU Boulder develops novel vacuum UV laser

16 Mar 2026

Offers potential to improve nanotechnology and power nuclear clocks.

Physicists at CU Boulder, Colorado, have demonstrated a new kind of vacuum ultraviolet laser, which they say is “100 to 1,000 times more efficient than existing technologies of its kind”. The source could enable scientists to observe phenomena currently out of reach for even the most powerful microscopes—such as following fuel molecules in real time as they undergo combustion, and spotting incredibly small defects in nanoelectronics.

The new laser might also allow for practical, ultraprecise nuclear clocks that rely on an energy transition in the nuclei of thorium atoms. These long sought-after devices could, theoretically, allow researchers to robustly track time with unprecedented precision.

The group is led by physicists Henry Kapteyn and Margaret Murnane, fellows of JILA, a joint research institute between CU Boulder and the U.S. National Institute of Standards and Technology (NIST). Jeremy Thurston, who earned his doctorate in physics from CU Boulder in 2024, led the work on the new laser.

“Scientists have been working toward vacuum ultraviolet lasers for decades,” said Kapteyn, a professor in the Department of Physics. “We think we have found a great route that can be scaled in power, and that is compact in size—two essential requirements for challenging applications.” The team is presenting its preliminary findings at the American Physical Society’s Global Physics Summit in Denver, Co., on March 17 and 19.

Murnane and Kapteyn’s laser is small enough to fit on top of an ordinary desk, and the researchers hope to make it even smaller and more efficient. “Shorter wavelengths matter because you can use them to make higher resolution microscopes,” said Murnane. “If a chemical reaction is happening, you can see what molecules are there—to see, for example, how they ablate the tiles on a space capsule as it reenters the atmosphere.”

Murnane, Kapteyn and their students are no stranger to powerful lasers. The researchers and their colleagues previously pioneered the design of tabletop X-ray lasers. These machines emit beams of light that oscillate more than a billion billion times per second.

Going deep

Laser scientists, however, have so far found it challenging to break into the vacuum ultraviolet, a region in between X-rays and visible light. All kinds of matter, from solids to atoms and organic molecules, interact strongly with vacuum ultraviolet light. “Basically, everything absorbs light at this range, which is why vacuum ultraviolet is so interesting and why it’s so difficult to engineer,” Kapteyn said. To get around those challenges, Kapteyn and Murnane’s group started with ordinary beams of red and blue laser light.

The team combined those beams in a special kind of chamber called an “anti-resonant hollow core fiber.” The fiber is similar to fiberoptic cables that transport optical communications data. This chamber, however, is made of a single hollow tube circled by seven smaller tubes.

Laser light passes through the central tube, and, in the process, collides with atoms of xenon gas. Those atoms absorb the light and reflect it – transforming the visible light into vacuum ultraviolet light. “To our knowledge, no other approach, either at big or small facilities, has the VUV power levels, tuning ranges and coherence that our new approach has shown,” said Murnane said.

He added that many technologies today are increasingly depending on nanoelectronics, or incredibly small devices. They include the semiconductors in the computer chips in phones, laptops and more. The team’s laser could help engineers optimize such devices—spotting tiny defects, for example, that could make them less efficient.