We propose a scheme to generate carrier-envelope-phase (CEP) stabilized few-cycle optical pulses from a free-electron laser oscillator. The CEP stabilization is realized by the continuous injection of CEP-stabilized seed pulses from an external laser to the free-electron laser oscillator whose cavity length is perfectly synchronized to the electron bunch repetition. Operated at a midinfrared wavelength, the proposed method is able to drive a photon source based on high harmonic generation (HHG) to explore the generation of isolated attosecond pulses at photon energies above 1 keV with a repetition of $>10\mathrm{MHz}$. The HHG photon source will open a door to full-scale experiments of attosecond x-ray pulses and push ultrafast laser science to the zeptosecond regime.

中文翻译：

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从自由电子激光振荡器生成载波包络相稳定的几个周期脉冲

我们提出了一种从自由电子激光振荡器生成稳定的载流子-相位相位（CEP）几个周期光脉冲的方案。通过从外部激光器向腔体长度与电子束重复完全同步的自由电子激光振荡器连续注入CEP稳定的种子脉冲，可以实现CEP稳定。该方法在中红外波长下运行，能够驱动基于高谐波产生（HHG）的光子源，以探测重复光子能量大于1 keV的孤立阿秒脉冲的产生。$>10\mathrm{兆赫}$。HHG光子源将为进行秒级X射线脉冲的全面实验打开一扇门，并将超快激光科学推向Zeptosecond领域。