2025/05/09 by Hao Sun, Jitao Sun, Sun, Hao +30
Engineering · Physics and Astronomy · #Accelerator Physics (physics.acc-ph) #FOS: Physical sciences #Laser-Matter Interactions and Applications #Particle Accelerators and Free-Electron Lasers #Quantum and Classical Electrodynamics
paper · pdf · doi:10.48550/arxiv.2505.05954
openalex publication_date 2025/05/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We report the experimental demonstration of direct-amplification enabled harmonic generation in an ultraviolet free-electron laser (FEL) driven by a low-intensity seed laser. By employing a versatile undulator configuration that enables seed amplification and harmonic generation within a unified setup, we achieved over 100-fold energy gain of the seed and observed exponential growth at the second harmonic. The results demonstrate that a sufficiently long modulator can not only amplify a weak seed but also induce strong energy modulation of the electron beam, enabling efficient harmonic bunching. This method markedly relaxes the power requirements on external seed lasers and presents a viable route toward high-repetition-rate, fully coherent FELs