Simultaneous Narrow-Band Temporal Pulse Shaping and Up-Conversion in Gas-Filled Hollow-Core Fibers

The primary limiting factor for XFEL brightness is the electron source, specifically the photoinjector. A common approach to increasing photoinjector brightness involves minimizing the transverse energy spread or emittance of the electron beam at the photocathode exit. This can be achieved through precise spatial and temporal shaping of the photoemission laser to mitigate non-linear space charge effects. Temporal pulse shaping is typically achieved using programmable modulators. However, this encounters challenges in the UV range, such as limited transparency, narrow bandwidth, and large losses. Here we present a new approach [1] to achieve precise control and generate the narrow-band-shaped pulse in the deep UV range by using the concept of spectral phase transfer in the gas-filled hollow-core fiber (HCF), which offers a high damage threshold, and the ability to handle extreme power levels.

[1] Zhang, Hao, et al. arXiv preprint arXiv:2404.16993 (2024).