Spatiotemporal shaping of attosecond X-rays with time-dependent orbital angular momentum

TL;DR

This paper introduces a novel method for spatiotemporal shaping of attosecond X-ray pulses by controlling their orbital angular momentum modes using an X-ray free-electron laser, enabling tunable, structured ultrafast X-ray sources.

Contribution

It presents a new approach to manipulate the spatiotemporal and topological properties of attosecond X-ray pulses via mode control in free-electron lasers, which was not previously demonstrated.

Findings

Demonstrates a double-spike waveform with different topological charges.

Shows tunable spike separation reaching several hundred attoseconds.

Provides a route for structured attosecond X-ray sources with controllable features.

Abstract

Attosecond X-ray pulses are indispensable for exploring ultrafast phenomena in matter on Angstrom and attosecond scales. Here we propose a new method to realize spatiotemporal shaping of attosecond X-rays through temporal control of the orbital angular momentum mode content using an X-ray free-electron laser. The method exploits transverse-mode-dependent frequency pulling in a deliberately detuned second stage, together with slippage between the seed and the amplified radiation. Three-dimensional simulations show a double-spike waveform in which the two spikes carry different dominant topological charges. The spike separation is tunable and can reach several hundred attoseconds. This provides a source-level route to spatiotemporally structured attosecond X-rays with controllable temporal structure and topological mode content.