Towards Predictive Modeling of Nonlinear Gas Optics for Xcimer's IFE Approach

Xcimer’s inertial fusion energy (IFE) hybrid drive concept [1] relies on laser pulses of unprecedented fluence, requiring precise beam shaping and temporal profiling. A critical component of this system is efficient pulse compression in gas via stimulated Brillouin scattering (SBS) and beam combining via stimulated rotational Raman scattering (SRRS). Operating in this nonlinear regime presents significant modeling challenges, including self-phase, filamentation, and phase distortion via gas turbulence. Our approach combines massively parallel high-order finite element methods, enabling accurate resolution of multi-scale physics. To further enhance fidelity and efficiency, we adopt a general phase transformation that enables a natural modeling of phase overcoming the discretization explosion, along with a co-moving frame transformation of coordinates that significantly reduces computational cost. Our results identify operating regimes that enable efficient SBS compression and SRRS beam combining while preserving phase and avoiding filamentation, informing the design of future high-fluence laser systems for IFE.



This work supports Xcimer’s mission to advance next-generation laser fusion, with simulation tools that inform optical system design, pulse shaping strategies, and risk mitigation for instabilities such as filamentation and stimulated scattering.

[1] C. A. Thomas, M. Tabak, N. B. Alexander, C. D. Galloway, E. M. Campbell, M. P. Farrell, J. L. Kline, D. S. Montgomery, M. J. Schmitt, A. R. Christopherson, and A. Valys. 2024. Hybrid direct drive with a two-sided ultraviolet laser. Physics of Plasmas 31, 11 (November 2024). DOI:https://doi.org/10.1063/5.0221201