Xcimer Energy Builds First Private Excimer Laser for Fusion in 20 Years
Xcimer Energy Builds First Private Excimer Laser for Fusion in 20 Years
Xcimer Energy has completed construction of the first electron-beam-pumped excimer laser built by a private company — and the first of its kind anywhere in more than 20 years. The company's laser, which uses the gas krypton fluoride, achieved a record pulse length of 3 microseconds in May 2024. This milestone marks the first major technical target Xcimer set out to hit for the U.S. Department of Energy's Milestone-Based Fusion Development Program.
The Denver-based company hit its DOE milestones three months ahead of schedule, fitting neatly into the federal government's broader effort to speed up commercial fusion development. Xcimer's approach builds on decades of work done by national laboratories and military research programs that explored laser-based fusion from the 1980s onward. The company is now positioning itself as one of the leading contenders in the race to make commercial laser fusion a reality.
How the Laser Works
Xcimer's system uses two types of excimer lasers — one that fires at 248 nanometers wavelength and another at 193 nanometers. Think of an excimer laser as a tool that fires very short, intense bursts of ultraviolet light. The shorter the wavelength, the more precisely that light can be focused. Xcimer is aiming to concentrate light energy at levels between 3 and 15 joules per square centimeter, with pulse durations ranging from 100 nanoseconds (billionths of a second) to 3 microseconds (millionths of a second).
The technology leans on research done over decades at government labs including the Naval Research Laboratory, Lawrence Livermore National Laboratory, and Los Alamos National Laboratory. Some of it even traces back to laser programs from the Cold War-era Strategic Defense Initiative. By combining those insights with new approaches to pumping the laser with electron beams instead of flashlamps, Xcimer believes it has found a path to higher efficiency.
The company is now building a new Denver facility that will house a prototype laser, including what Xcimer calls the world's largest nonlinear optical pulse compression system — essentially a highly specialized optical setup that can squeeze laser pulses into tighter time windows. This prototype is meant to be a proof-of-concept before moving toward Phoenix, a larger demonstration system, and finally Athena, which Xcimer envisions as the world's first laser fusion power plant.
Funding and Government Support
The U.S. Department of Energy has approved federal funding for Xcimer's project, called HYPER-LASER, under its ARPA-E program. ARPA-E (Advanced Research Projects Agency-Energy) is a federal office that funds high-risk, high-reward energy technology projects. The government's backing validates Xcimer's technical approach, though federal funding is tied to hitting specific milestones rather than traditional grant disbursements — meaning the company only gets money when it reaches agreed-upon targets.
According to the Department of Energy, if Xcimer's technology development succeeds, laser fusion power plants could be deployed by the mid-2030s. Xcimer is one of eight companies selected for this milestone-based fusion funding program, which represents a shift in how the federal government supports experimental energy technologies.
Private Money and Team Growth
In parallel with government support, Xcimer raised $100 million in Series A funding led by Hedosophia, a venture capital firm focused on deep-technology companies. Other investors include Breakthrough Energy Ventures, Lowercarbon Capital, Prelude Ventures, Emerson Collective, Gigascale Capital, and Starlight Ventures. This combination of private and public backing is now a familiar pattern in emerging energy technology, though it remains a relatively new approach.
The company is expanding its leadership team and plans to double its headcount over the next year as it moves from the prototype phase toward scaled manufacturing. Key recent hires include Douglas Kunzman as Vice President of Defense programs, Justin Brynestad as Senior Vice President for the Vulcan program, and Brad Appel as Chief Engineer for Vulcan.
The Bigger Picture
The fusion energy field has become crowded over the past five years, with dozens of private companies pursuing different technical paths. Commonwealth Fusion Systems and others are pursuing magnetic confinement — essentially using powerful magnets to hold super-hot plasma. Xcimer instead builds on the laser-based approach, similar to the method that the National Ignition Facility used when it achieved fusion ignition in 2022.
The broader context here is worth noting. The combination of federal milestone funding paired with substantial private venture capital mirrors a playbook that worked well in commercial spaceflight during the 2000s and 2010s. SpaceX and Blue Origin were first to prove that private companies could build cutting-edge rocket technology when government funding was structured around achievements rather than open-ended grants, and private capital filled in the gaps for scaling. That same pattern is now being applied to fusion energy, and Xcimer is one of the companies testing whether it will work again.
The 20-year gap since the last electron-beam excimer laser was built by anyone — government or private sector — tells you something important. These are complicated machines, and there has been almost no commercial reason to build them until now. Xcimer's success in completing one validates that the manufacturing knowledge, largely locked away in laboratory reports and government archives, can be translated into real hardware. That is a tangible step forward, even if the full path to a working power plant remains unproven.
Significant engineering challenges remain between Xcimer's current prototype and a laser system that could actually power a grid-scale facility. The company still needs to demonstrate that its laser-fusion approach can generate more energy than it consumes, that it can operate reliably and repeatedly, and that the whole system can eventually be built cheaply enough to compete with wind, solar, and other clean energy sources. Those are formidable problems, but Xcimer has cleared the first hurdle.
