We demonstrate free-beam spectral self-compression of ~100-GW femtosecond laser pulses due to self-phase modulation (SPM) in a transparent dielectric. While all the earlier studies of SPM-induced spectral narrowing have been performed using optical fibers, experiments and simulations presented in this Letter show that this type of spectral transformation can be implemented as a part of a full three-dimensional field-waveform dynamics and can be extended to peak powers $\sim {10}^5$ times higher than the critical power of self-focusing. With a properly chosen initial chirp, spectral self-compression is accompanied by pulse compression, providing spectral–temporal mode self-compression as a whole.

中文翻译：

---

超临界峰值功率下的自由束频谱自压缩

我们展示了由于透明电介质中的自相位调制（SPM）而导致的〜100 GW飞秒激光脉冲的自由光束光谱自压缩。尽管已经使用光纤对SPM引起的光谱变窄进行了所有较早的研究，但在本信函中提出的实验和模拟表明，这种类型的光谱变换可以作为完整的三维场波形动力学的一部分来实现，并且可以扩展到峰值功率$〜{10}^5$比自我聚焦的关键能力高出十倍。用适当选择的初始啁啾，光谱自压缩是伴随着脉冲压缩，提供频谱 - 时间模式的自我压缩为一个整体。