Fusion startup Xcimer Energy reportedly activated its Phoenix laser system in Denver, claiming the title of the world’s largest privately owned laser. The 38-metre-long machine is described as a deliberate step toward a commercial fusion power plant the company aims to build in the mid-2030s.
What Phoenix actually is
Phoenix is described as the first electron-beam-pumped excimer laser built in the private sector, and the first of its kind constructed by any organisation in more than two decades. At full strength, its krypton-fluoride core reportedly generates over 1 kilojoule of energy. That figure sits orders of magnitude below the more than 12 megajoules estimated for a commercial-scale plant, but Phoenix is not designed to ignite fuel. It is designed to prove a manufacturing and physics architecture.
The system validates two specific bets. The first is long-pulse excimer operation, which the company argues unlocks meaningful cost reductions versus the solid-state lasers used at the U.S. government’s National Ignition Facility. The second is a pulse compression method known as Stimulated Brillouin Scattering, used to compress microsecond pulses down to nanoseconds without damaging the optics.
The NIF reference point
Xcimer’s approach is modelled on the National Ignition Facility, which in December 2022 became the first facility to demonstrate that a controlled fusion reaction could release more energy than the laser input required to ignite it. NIF achieved this by training 192 laser beams on a fuel target smaller than a pencil eraser, converting that energy into X-rays that compress the fuel pellet until atoms fuse.
The NIF, however, was built as a nuclear weapons stewardship facility, not a power plant. Its solid-state laser system fires roughly once a day. A commercial fusion reactor would need to fire several times per second, every second, for years. That gap between scientific demonstration and industrial operation is the gap Xcimer is attempting to close — and it is also the gap that has historically swallowed fusion startups.
Why excimer, and why now
Excimer lasers are not exotic. They are the workhorse of deep-ultraviolet photolithography, the process by which microchips are manufactured. Current lithography tools rely on krypton-fluoride and argon-fluoride excimer lasers at 248 and 193 nanometres — the same chemistry Xcimer is scaling up by many orders of magnitude.
That genealogy matters. The supply chain, optics expertise, and gas-handling engineering for excimer systems already exist at industrial scale because the semiconductor industry built them over decades. Silicon Canals has reported on ASML’s lithography monopoly, and the world’s most advanced laser-based manufacturing systems trace directly to this same excimer lineage. Xcimer is, in effect, repurposing the industrial base of chipmaking and pointing it at the power grid.
The institutional logic
Private fusion has attracted significant capital over the past several years on the premise that government-scale physics can be reproduced at startup economics. Xcimer’s pitch sharpens that premise: rather than build something exotic, build something the global semiconductor supply chain already understands, and bet the savings on simpler, more powerful lasers.
The roadmap remains long. A working prototype is reportedly targeted for 2028, followed by a larger system intended to reach scientific break-even, and a first commercial-scale plant in the mid-2030s. Between Phoenix’s 1 kilojoule and a plant’s 12 megajoules sit roughly four orders of magnitude — and every previous fusion timeline in history has slipped.
