- The paper demonstrates a novel method using bichromatic light in a FERMI seeded FEL to achieve attosecond phase control.
- The experimental setup employs dual photon frequencies to precisely manipulate electron angular distributions, confirming a 105 attosecond oscillation period.
- The findings pave the way for advanced attosecond spectroscopic techniques with significant implications for quantum dynamics and materials research.
Coherent Control with a Short-Wavelength Free Electron Laser
The paper, titled "Coherent Control with a Short-Wavelength Free Electron Laser," explores the innovative application of coherent control in the context of Extreme Ultraviolet (XUV) and X-ray Free Electron Lasers (FELs). The authors present a methodology to achieve coherent control using a FERMI seeded FEL system, employing bichromatic light to generate and manipulate two-color phase coherence with unprecedented attosecond temporal resolution.
Coherent control has traditionally been a domain of long-wavelength optical techniques, aiming to drive quantum systems to desired states by manipulating the phase and wavelengths of the involved laser fields. The fundamental challenge in applying this technology to XUV and X-ray regions arises from constraints in achieving high longitudinal coherence and phase control. The paper describes addressing these challenges through the use of phase-locked, two-color emission generated by the FERMI FEL. Specifically, by leveraging the delay line capability, researchers achieved a temporal resolution down to 3.1 attoseconds, allowing precise manipulation of phase differences between harmonics.
The experimental setup described entails the use of two photon frequencies—63.0 nm and 31.5 nm—produced by the FEL to ionize neon atoms and manipulate the photoelectron angular distribution by controlling phase differences. This phase control is critical, as demonstrated by evident oscillations in the angular distributions of emitted electrons. These angular distributions were further analyzed using velocity map imaging (VMI) spectrometry to establish the robust correlation between phase control and electron distribution asymmetry.
The numerical results provide compelling evidence of the capability to perform coherent control operations on XUV wavelengths with high precision. The paper reports that the oscillation period observed was consistent with the theoretical predictions, displaying a period of 105 attoseconds, with measurements indicating a resolution of 3.1 attoseconds. This phase control is significant for photoelectron spectroscopy and quantum dynamic studies. The asymmetry parameter, measured as a function of phase difference, demonstrated clear oscillations, confirming the successful manipulation of electron distributions.
This advancement holds significant implications for research areas requiring ultra-fast processes and chemical selectivity, such as studies in femtochemistry, catalysis, photosynthesis, and materials science. The capability to target specific electronic core levels—achievable due to the short XUV wavelengths—allows for investigations into chemical bond dynamics and electron motion in more complex systems than previously possible.
Furthermore, the potential future applications of this technology are promising. The demonstrated technique could inform the development of new experimental approaches in attosecond science, including pulse shaping and sculpting in the XUV domain. In particular, these findings could be adapted for use in Solid-State Amplifier-based Self-Amplified Spontaneous Emission (SASE) FELs, to extend coherent control techniques over a broader range of wavelengths.
Overall, this paper provides a substantial contribution to the field of quantum control and coherent light-matter interaction, paving the way for future explorations at the intersection of ultrafast spectroscopy and nanoscience.