Full-Time

Laser Plasma Interaction Computational Physicist

Xcimer Energy

Xcimer Energy

51-200 employees

Develops inertial fusion power using laser

Compensation Overview

$170k - $210k/yr

No H1B Sponsorship

Denver, CO, USA

In Person

US Citizenship Required

PhD

Category
Academic & Institutional Research
Required Skills
Python
Git
C/C++

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Requirements
  • Education: PhD in Computational Physics, Plasma Physics, Applied Physics, or a closely related technical field.
  • Strong software development skills in scientific computing using modern C++ and Python.
  • Experience developing physics simulation codes with emphasis on modular software architecture, maintainability, and software quality.
  • Strong understanding of laser plasma interaction physics, collisional plasma kinetics, and laser propagation models.
  • Familiarity with numerical methods for partial differential equations, kinetic plasma simulations, and/or paraxial wave equations.
  • Experience using, extending, or validating community simulation tools such as particle-in-cell (PIC) or fluid plasma codes.
  • Experience working independently and leading technically complex software development efforts.
  • Must be a U.S. citizen or national, U.S. permanent resident (current Green Card holder), or lawfully admitted into the U.S. as a refugee or granted asylum.
Responsibilities
  • Deploy, configure, and extend existing simulation tools such as WarpX and LPSE to model laser plasma interaction phenomena relevant to Xcimer’s laser architecture.
  • Develop workflows, simulation setups, post-processing pipelines, and benchmarking methodologies for efficient and repeatable simulation execution.
  • Lead the design and development of in-house LPI simulation software focused on collisional kinetics and paraxial laser propagation models.
  • Architect simulation software using modular, extensible, and maintainable scientific software frameworks with strong emphasis on composability and long-term scalability.
  • Implement and validate core physics models including collisional plasma kinetics, paraxial laser propagation, stimulated Raman scattering (SRS), stimulated Brillouin scattering (SBS), filamentation, and cross-beam energy transfer (CBET).
  • Perform verification, convergence studies, and benchmarking against existing tools, published results, and experimental data to ensure numerical robustness and model credibility.
  • Optimize simulation software for high-performance computing environments, including parallelization and scalability across modern compute architectures.
  • Maintain rigorous software engineering practices including version control, automated testing infrastructure, documentation, and reproducibility standards.
  • Collaborate cross-functionally with laser architecture, gas optics, radiation hydrodynamics, experimental physics, and other engineering teams to prioritize simulation efforts and integrate modeling outputs into broader system development activities.
  • Contribute to Xcimer’s long-term computational modeling strategy by identifying opportunities to integrate new physics capabilities and couple simulation domains through shared modular architectures.
Desired Qualifications
  • Experience with WarpX, LPSE, pF3D, or similar laser plasma interaction simulation tools.
  • Experience with high-performance computing, including MPI/OpenMP parallelization and/or GPU acceleration.
  • Familiarity with modern scientific software architectures including plugin systems, composable frameworks, or modular physics engines.
  • Experience within inertial confinement fusion (ICF), high-energy-density physics, or advanced plasma modeling environments.
  • Demonstrated experience building extensible scientific software platforms that support long-term collaboration and multi-user development.

Xcimer Energy develops inertial fusion energy technology aiming to generate fusion-powered electricity. Its system uses a 10+ megajoule KrF laser to ignite a hydrogen fusion target inside a HYLIFE-style liquid-wall chamber, which absorbs fusion energy and shields reactor walls for long life. The approach combines a high-energy laser, a consumable fusion target, and a liquid-wall chamber to pursue scalable, laser-driven inertial confinement fusion for power generation. The company’s goal is to make commercial fusion power a reality for utilities within the next decade.

Company Size

51-200

Company Stage

Series A

Total Funding

$117.8M

Headquarters

Denver, Colorado

Founded

2021

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Simplify Jobs

Simplify's Take

What believers are saying

  • Xcimer raised $100 million in June 2024 and nearly $200 million total.
  • The company expanded Denver in May 2026 and planned to double headcount.
  • DOE funding, June 2026 approval, and RTX backing improve financing and recruiting access.

What critics are saying

  • Vulcan site selection slipped past 2025; further delays push commercialization beyond 2035.
  • Athena needs multi-megajoule lasers, tritium breeding, and grid integration before any revenue.
  • Any Phoenix-to-Anvil performance miss would strand Xcimer’s capital-intensive laser platform.

What makes Xcimer Energy unique

  • Xcimer’s June 2026 DOE-approved Athena roadmap validates its KrF inertial-fusion architecture.
  • Phoenix started operations June 3, 2026, proving 1-kJ excimer amplification and 38-meter SBS compression.
  • RTX partnered September 9, 2026, giving Xcimer defense-market validation beyond fusion alone.

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Benefits

Health Insurance

Dental Insurance

Vision Insurance

Life Insurance

Disability Insurance

401(k) Company Match

Paid Vacation

Paid Sick Leave

Paid Holidays

Company Equity

Growth & Insights and Company News

Headcount

6 month growth

-2%

1 year growth

-1%

2 year growth

0%
Associated Press
Sep 10th, 2026
RTX invests in Xcimer Energy to develop laser fusion technology for air defense systems

RTX Ventures has made a minority investment in Xcimer Energy Corporation to support development of scalable pulsed-laser technologies. Xcimer has raised nearly $200 million from investors including Hedosophia and Breakthrough Energy Ventures. The companies signed a teaming agreement to explore integrating Xcimer's laser technology into RTX's defence systems for defeating airborne threats. Xcimer's fusion pilot power plant design was approved by the US Department of Energy in June as part of the Milestone-based Fusion Development Program. The excimer laser system aims to deliver longer-range performance at lower cost than current directed energy systems. Xcimer expects to deliver fusion energy to the grid by the mid-2030s. RTX's chief technology officer Juan de Bedout said the partnership will explore integrating Xcimer's technology with RTX's expertise in advanced sensing and air defence.

Business Wire
Jun 10th, 2026
DOE approves Xcimer's fusion power plant design, clears path to commercial laser fusion

Xcimer Energy has secured US Department of Energy approval for its preconceptual design and technology roadmap for Athena, its fusion power plant architecture. The milestone, part of the DOE's Fusion Milestone Development Program, positions the Denver-based startup amongst frontrunners to commercialise fusion energy. Xcimer's 724-page submission detailed plant performance targets, economics, engineering requirements, safety analyses and development pathways. Athena integrates the company's proprietary excimer laser platform with target delivery, fusion chamber, tritium breeding and power generation systems designed for industrial scale. The approval follows Xcimer's launch of Phoenix, the world's largest privately owned laser system, at its 74,000-square-foot Denver facility. Founded in 2022, Xcimer is developing laser fusion technology targeting costs under $100 per joule with a chamber design requiring no first-wall replacement.

TechCrunch
Jun 3rd, 2026
World's largest privately owned laser switched on by fusion startup Xcimer Energy

Fusion startup Xcimer Energy has activated its Phoenix laser system, which the company claims is the world's largest privately owned laser. The system uses excimer amplification to generate over one kilojoule of energy through a 38-metre-long krypton-fluoride laser core. Xcimer's approach mirrors the National Ignition Facility, which in December 2022 demonstrated a controlled fusion reaction producing more power than required to ignite it. The company aims to improve upon this concept using more powerful, less complex lasers that compress fuel targets in nanoseconds rather than microseconds. Phoenix represents an early step towards a commercial fusion power plant, which Xcimer estimates would require lasers exceeding 12 megajoules. The company plans to complete a prototype by 2028 and build its first commercial-scale power plant in the mid-2030s.

Business Wire
May 12th, 2026
Xcimer Energy hires defence VP as fusion startup scales team to 400 amid $90M facility build

Xcimer Energy has hired Doug Kunzman as Vice President of Defence as the Denver-based fusion startup scales towards commercial operations. Kunzman brings extensive military and aerospace experience, including commanding US Navy warships and leading operations at Blue Origin and Astra. The company, which now employs nearly 200 people, plans to double its workforce over the next year to advance Vulcan, its next-generation laser fusion facility. Xcimer is developing excimer-laser architecture for scalable inertial fusion energy with applications in energy resilience and national security. Recent leadership additions include Brad Appel as Chief Engineer for Vulcan, previously CTO at Ursa Major and SpaceX; Justin Brynestad as Senior Vice President overseeing Vulcan programme execution; and Rachel Konrad as Senior Vice President of Strategic Communications. Founded in 2022, Xcimer has secured Department of Energy funding.

Business Wire
Jun 6th, 2024
Xcimer Raises $100 Million to Put Inertial Fusion Energy on Path to Commercialization

Xcimer Energy Inc. today announced that it has raised $100 million in Series A financing led by Hedosophia, with participation from investors includin