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arXiv · 2505.05954

Demonstration of Direct-amplification Enabled Harmonic Generation in an Ultraviolet Free-Electron Laser

Hao Sun·Jitao Sun·Li Zeng·Yifan Liang·Lingjun Tu·Huaiqian Yi·Qinming Li·Xiaofan Wang·Yong Yu·Jiayue Yang·Zhigang He·Yuhuan Tian·Likai Wang·Zequn Wang·Guorong Wu·Weiqing Zhang·Xueming Yang
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Abstract

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

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Hao Sun, Jitao Sun, Li Zeng, Yifan Liang, Lingjun Tu, Huaiqian Yi, Qinming Li, Xiaofan Wang, Yong Yu, Jiayue Yang, Zhigang He, Yuhuan Tian, Likai Wang, Zequn Wang, Guorong Wu, Weiqing Zhang, Xueming Yang. 2025-05-09. Demonstration of Direct-amplification Enabled Harmonic Generation in an Ultraviolet Free-Electron Laser. https://arxiv.org/abs/2505.05954

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