Spectral-phase interferometry for direct electric-field reconstruction applied to seeded extreme-ultraviolet free-electron lasers

TL;DR

This paper introduces a simple spectral-phase interferometry method for directly reconstructing the electric field of femtosecond pulses from seeded free-electron lasers in the extreme-ultraviolet, enabling better control and understanding of FEL outputs.

Contribution

It demonstrates a practical setup for complete pulse characterization of FELs in the EUV using SPIDER, facilitating improved diagnostics and control of FEL spectral phase.

Findings

Successfully reconstructs FEL pulse shape and phase using SPIDER

Simple seed laser arrangement enables practical implementation

Simulation results confirm accurate phase retrieval

Abstract

We present a setup for complete characterization of femtosecond pulses generated by seeded free-electron lasers (FEL's) in the extreme-ultraviolet spectral region. Two delayed and spectrally shifted replicas are produced and used for spectral phase interferometry for direct electric field reconstruction (SPIDER). We show that it can be achieved by a simple arrangement of the seed laser. Temporal shape and phase obtained in FEL simulations are well retrieved by the SPIDER reconstruction, allowing to foresee the implementation of this diagnostic on existing and future sources. This will be a significant step towards an experimental investigation and control of FEL spectral phase.