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Optimized laser wakefield acceleration: Generating stable, high-energy, monoenergetic electron beams and demonstrating extreme-ultraviolet free-electron lasers

Zhan Jin1,3,*, Masaki Kando2,3,1,†, Yan-Jun Gu1,3, Kai Huang2,3, Nobuhiko Nakanii2,3, Izuru Daito2, Zhenzhe Lei1, Shingo Sato1, Hiroaki Sano1 et al.

Toshiya Muto1, Shigeru Yamamoto4,3, and Tomonao Hosokai1,3

  • *Contact author: jin@sanken.osaka-u.ac.jp
  • †Contact author: kando.masaki@qst.go.jp
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Phys. Rev. Research 8, 013207 – Published 24 February, 2026

DOI: https://doi.org/10.1103/qvg7-ng8n

Abstract

Free electron lasers (FELs) are powerful, tunable light sources capable of delivering ultrashort, coherent radiation over a wide spectral range, but their broad scientific and technological impact is limited by the size and cost of large-scale accelerators. Laser wakefield acceleration (LWFA) offers a compact alternative via the ultrahigh accelerating gradients, though achieving FEL gain with such beams remains a major challenge due to the stringent beam-quality requirements. Here, we present a successful demonstration of a laser-plasma accelerator-driven FEL operating at a central wavelength of 40nm with a highly nonlinear gain. A compact 0.8J laser system, combined with precise control over the plasma-density profile, injection conditions, and the stability of both laser wave front and gas jet, enabled the generation of high-quality monoenergetic electron beams with excellent shot-to-shot reproducibility. A comprehensive start-to-end simulation framework was established, incorporating beam acceleration, transport, and FEL generation. Each stage of the simulation shows good agreement with the experimental diagnostics. The resulting FEL radiation exhibits clear exponential gain of approximately 20 times. This work highlights a reliable route toward compact, tunable, x-ray FELs driven by LWFA, and represents a significant step toward practical applications of laser-plasma-based light sources.

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Phys. Rev. Research 8, 013207– Published 24 February, 2026
  • Received 23 July 2025
  • Accepted 6 January 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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