# Coherent control with a short-wavelength Free Electron Laser

## TL;DR

This paper demonstrates phase-controlled two-color coherent control using a short-wavelength Free Electron Laser, enabling ultrahigh time resolution and chemical sensitivity in experiments like ionization.

## Contribution

It shows for the first time phase correlation and control of two-color FEL pulses at short wavelengths, overcoming previous coherence limitations.

## Key findings

- Phase correlation of two colors demonstrated at 63.0 and 31.5 nm.
- Controlled photoelectron angular distribution asymmetry via phase adjustment.
- Achieved 3-attosecond temporal resolution in control experiment.

## Abstract

XUV and X-ray Free Electron Lasers (FELs) produce short wavelength pulses with high intensity, ultrashort duration, well-defined polarization and transverse coherence, and have been utilised for many experiments previously possible at long wavelengths only: multiphoton ionization, pumping an atomic laser, and four-wave mixing spectroscopy. However one important optical technique, coherent control, has not yet been demonstrated, because Self- Amplified Spontaneous Emission FELs have limited longitudinal coherence. Single-colour pulses from the FERMI seeded FEL are longitudinally coherent, and two-colour emission is predicted to be coherent. Here we demonstrate the phase correlation of two colours, and manipulate it to control an experiment. Light of wavelengths 63.0 and 31.5 nm ionized neon, and the asymmetry of the photoelectron angular distribution was controlled by adjusting the phase, with temporal resolution 3 attoseconds. This opens the door to new shortwavelength coherent control experiments with ultrahigh time resolution and chemical sensitivity.

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Source: https://tomesphere.com/paper/1701.03387