[论文解读] Demonstration of High-Gain Harmonic Lasing in a Terahertz Free-Electron Laser

Yin Kang, Cheng Yu+27 more|arXiv (Cornell University)|Feb 14, 2026

Particle Accelerators and Free-Electron Lasers被引用 0

一句话总结

本文首次在太赫兹自由电子激光器（FEL）中实验验证了高增益谐波激光的实现，能够在第3和第5谐波实现持续放大，输出功率与基频操作相当，并扩展了光谱覆盖范围。

ABSTRACT

Compact Free-Electron Lasers (FELs) offering broad, continuous spectral tunability are traditionally constrained by fixed-parameter magnetic structures and the necessity for high-energy electron beams. High-gain Harmonic Lasing (HL) has long been proposed as a solution to overcome these limitations; however, a robust experimental verification of this principle has remained absent. Here, we report the first experimental demonstration of high-gain HL. By employing a frequency-tunable electron beam density modulation to dominate the fundamental instability, we achieved sustained FEL amplification at the 3rd and 5th harmonics of the wiggler. The HL mode generated output power comparable to conventional fundamental operation with enhanced stability and narrower spectral bandwidth. Notably, we demonstrate that HL extends the spectral coverage by a factor of two under fixed facility constraints, achieving pulse energies up to 540 μJ. These results establish high-gain HL as a versatile mechanism for advancing compact, wavelength-flexible FEL facilities.

研究动机与目标

• 激励并测试高增益谐波激光（HL）以克服紧凑FEL中的固定参数磁结构与高能束流约束。
• 证明可以主导基频不稳定性的频率可调电子束密度调制。
• 在现实、固定设施约束下，展示在wiggler的第3和第5谐波下的持续FEL放大。

提出的方法

• 使用频率可调的电子束密度调制来抑制基频不稳定性并促进HL。
• 操作太赫兹FEL以在wiggler的第3和第5谐波实现放大。
• 在稳定性、谱带宽和输出功率方面，将HL模式性能与常规基频操作进行对比。
• 在固定设施约束下证明HL将光谱覆盖范围扩展两倍。
• 测量HL操作下的脉冲能量高达540 μJ。

实验结果

研究问题

• RQ1 HL是否能够在太赫兹FEL中在第3和第5谐波实现鲁棒的高增益放大？
• RQ2 在固定设施约束下，HL是否扩展紧凑FEL的光谱覆盖同时保持稳定性？
• RQ3 HL的输出功率、稳定性和光谱带宽与传统基频操作相比如何？

主要发现

• 在wiggler的第3和第5谐波实现了持续的FEL放大。
• HL模式的输出功率可与传统基频操作相当。
• HL显示出增强的稳定性和更窄的光谱带宽。
• 在固定设施约束下，光谱覆盖扩大了一倍。
• HL操作的脉冲能量达到高达540 μJ。