A Denver startup designing the world's largest excimer laser system to drive inertial fusion energy, betting that cheap, efficient gas lasers can solve the economics that have stalled laser fusion since the 1970s.
The National Ignition Facility proved that laser-driven inertial confinement fusion can produce net energy gain, but NIF's 192-beam solid-state laser system cost roughly $3.5 billion and fires at most a few times per day. For a power plant, the lasers must fire ten times per second, last for decades, and cost a fraction of NIF's price tag. Xcimer Energy, founded in 2022 and based in Denver, Colorado, believes excimer lasers -- gas-phase lasers that use noble-gas halide molecules like krypton fluoride (KrF) -- are the answer. The company was co-founded by Conner Galloway (CEO) and Dr. Stephen Obenschain, a veteran laser-fusion physicist who spent decades developing KrF laser technology at the Naval Research Laboratory (NRL).1
KrF excimer lasers produce ultraviolet light at 248 nanometers, a shorter wavelength than NIF's frequency-tripled 351-nanometer beams. Shorter wavelengths couple more efficiently to fusion targets and suppress laser-plasma instabilities that degrade implosion symmetry. Excimer lasers also amplify light through a gas medium that is inherently cheaper and more easily replaced than the large glass slabs used in solid-state systems. The NRL demonstrated these advantages experimentally on its Nike and Electra laser systems over three decades of research. Xcimer's innovation is architectural: rather than building many small beamlines, the company is designing a single enormous amplifier cavity in which the laser pulse bounces back and forth through the gain medium, extracting energy on each pass.3
Xcimer raised a $100 million Series A round in early 2024, one of the largest early-stage raises in private fusion history. Investors include Breakthrough Energy Ventures, Lowercarbon Capital, Prelude Ventures, and Congruent Ventures. The DOE selected Xcimer for its milestone-based Fusion Milestone Program in 2024, providing additional public funding tied to technical demonstrations. The company is building its first prototype laser system at its Denver facility and has recruited engineers from NIF, NRL, and the broader laser-physics community.4
Excimer lasers have never been built at the scale Xcimer envisions. The single-cavity architecture is novel and unproven at megajoule energies. Repetition-rate durability -- firing a gas laser ten times per second for years -- presents materials and optical challenges that NRL's research-scale systems did not need to solve. Target fabrication and injection at matching rates add further engineering hurdles shared with all inertial fusion approaches. Xcimer's cost projections are modeled, not measured, and the gap between a laboratory KrF laser and a power-plant-scale system is substantial. The $100 million raise and DOE partnership provide significant runway, but the company is still years from an integrated laser-target experiment.5