Xcimer Energy completes first private-sector electron-beam excimer laser

12 Jun 2025

Denver-based inertial fusion startup’s laser is first of its kind built by any organization in more than 20 years.

Inertial fusion startup Xcimer Energy has announced it has completed what it calls the world’s first electron-beam-pumped excimer laser funded by the private sector. The laser is also said to be the first built by any organization, including federal labs, in more than 20 years.

The system operates at the longest pulse length of any krypton fluoride (KrF) laser. In May, the laser achieved a pulse length of 3 microseconds – a record for this type of laser.

Xcimer’s Long Pulse Kinetics (LPK) platform is the first key element of its prototype laser system, code-named Phoenix, which is on track to be completed in 2026, the company said. The LPK collects data that proves the viability of Xcimer’s technology and informs future design of its lasers that will power inertial fusion energy systems.

The company submitted a report on its LPK system to the U.S. Department of Energy’s Milestone-Based Fusion Development Program, three months ahead of schedule. Completion and operation of the LPK represents Xcimer’s first major technical milestone in the program. The Fusion Development Program is modeled in part after the NASA Commercial Orbital Transportation Services (COTS) program, which unleashed private companies to meet early technical milestones on the way to building today’s commercial space-launch industry.

“We’ve already begun using Xcimer’s LPK experimental testbed to validate laser models and inform the design of our future systems,” commented Conner Galloway, CEO and Chief Science Officer of Xcimer. “This milestone also sends the strongest signal yet that the private sector can build on decades of public investment to turn transformative research into commercially viable systems.”

Xcimer’s goal for 2030 is to complete the construction of Vulcan, its next-generation facility that will be designed to achieve the highest laser energy in the world using the largest laser amplifiers ever built, which will be designed based on data from LPK. The roadmap includes putting the first inertial fusion power plants delivering electricity to the grid as soon as the mid-2030s, the company stated.

The company’s announcement added, “Xcimer is already taking proposals on prospective new sites nationwide to house Vulcan, which would directly employ hundreds of people in a large variety of jobs, including physicists, technicians, and support staff. Vulcan’s location could pave the way for a future regional source of zero-carbon energy expertise.”

Toward fusion energy

Xcimer is developing what some experts say is the most economically viable path to delivering virtually limitless, carbon-free energy, adapting the only fusion approach that has been experimentally demonstrated to exceed scientific breakeven. This capability, the company says, “has the potential to power energy-intensive technologies across sectors including AI, robotics, healthcare, transportation, desalination, manufacturing, and space exploration”.

Compared to other fusion companies, Xcimer says it has superior long-term economics due to the decoupled nature of the subsystems, higher fuel burnup fraction, and ability to directly protect the first structural wall with the molten salt flow so that it can last the entire lifetime of a power plant.

Founded a year prior to the NIF breakthrough in December 2022, Xcimer is building a laser architecture, which, it says, “will affordably produce up to 10 times more laser energy at 10 times higher efficiency than the NIF system while bypassing the optics damage issues inherent in NIF-like architectures.” While excimer lasers are widely used in semiconductor lithography, medical and industrial applications, Xcimer will be the first company to apply them to fusion energy generation at scale.

The firm has raised just over $111 million from leading energy investors since its founding in 2022. Its approach is part of the DOE Milestone-Based Fusion Development Program, a highly competitive public-private partnership program designed to accelerate the development of fusion energy on the power grid. Xcimer was awarded $9 million, one of the most significant awards under the program’s first budget period.