Mode-Locking in a Free-Electron Laser Amplifier

TL;DR

This paper proposes a novel technique for generating attosecond pulse trains in free-electron lasers by synthesizing and phase-locking longitudinal modes, enabling ultra-short, high-power X-ray pulses.

Contribution

It introduces a new optics-free method to produce phase-locked mode trains in FELs, achieving attosecond pulse generation at unprecedented power levels.

Findings

Generation of 400as pulse trains at 124 Å with giga-watt power.

Prediction of 23as pulse trains at 1.5 Å with peak power up to 6GW.

Demonstration of mode-locking via electron beam energy modulation.

Abstract

A technique is proposed to generate attosecond pulse trains of radiation from a Free-Electron Laser amplifier. The optics-free technique synthesises a comb of longitudinal modes by applying a series of spatio-temporal shifts between the co-propagating radiation and electron bunch in the FEL. The modes may be phase-locked by modulating the electron beam energy at the mode spacing frequency. Three-dimensional simulations demonstrate the generation of a train of 400as pulses at giga-watt power levels evenly spaced by 2.5fs at a wavelength of 124 Angstrom. In the X-ray at wavelength 1.5 Angstrom, trains of 23as pulses evenly spaced by 150as and of peak power up to 6GW are predicted.