Enhancing High-Power Gas Lasers Output via Hybrid Pumping for Inertial Confinement Fusion Applications

The development of efficient, reliable, and cost-effective high-energy laser systems is a critical milestone for realizing commercial-scale laser fusion energy. Historically, high-power gas lasers such as the rare-gas halide excimer lasers (e.g., KrF and ArF) have relied solely on relativistic electron beams (e-beams) for pumping, despite their inherent inefficiencies, foil degradation issues, and substantial infrastructure costs. We present a novel hybrid pumping architecture that combines a pulsed electromagnetic (EM) source, such as microwave, millimeter-wave, or infrared radiation, with a dedicated electron source to decouple the tasks of plasma maintenance and upper laser level excitation.

In this scheme, the electron source maintains the required electron density in the gain medium, while the EM radiation heats thermalized (“cold”) electrons via inverse Bremsstrahlung to energy levels (~10–20 eV) optimal for impact excitation of rare gas atoms. This approach directly addresses the fundamental inefficiency in conventional systems where most e-beam electron energies vastly exceed the excitation thresholds and are thus poorly matched to the kinetic requirements of the laser medium. By “recycling” these cold electrons and carefully controlling both their density and energy distribution, the hybrid method improves the efficiency of coupling power into the upper laser level, lowers cost significantly because of the reduced dependence on (or elimination of) e-beam systems, and offers flexibility through control of the relative timing of the EM radiation and electron source pulses.

Simulations and design considerations suggest that this hybrid scheme can significantly enhance the efficiency of excimer lasers, potentially exceeding the ~7% ceiling of traditional e-beam systems. The proposed system architecture also allows for modular expansion and supports resonant cavity configurations to further optimize EM field delivery to the laser plasma. These advances hold promise for scalable, MJ-class UV laser systems capable of supporting the energy demands of next-generation inertial confinement fusion plants.