Generation Dynamics of Broadband Extreme Ultraviolet Vortex Beams.

Area of Science:

• Quantum Optics
• Laser Physics
• Attosecond Science

Background:

• High harmonic generation (HHG) enables the production of extreme ultraviolet and soft X-ray light beams with orbital angular momentum (OAM).
• The phase properties of the driving laser are imprinted onto the HHG beams, alongside the inherent dipole phase.
• The nonlinear nature of HHG and the rapid phase variations in OAM beams create high sensitivity to the driving field.

Purpose of the Study:

• To overcome the challenge of accurately reconstructing multiwavelength OAM beams from HHG.
• To investigate the influence of generation conditions and drive laser aberrations on vortex beam properties.
• To enable detailed multiwavelength beam reconstructions for understanding OAM generation dynamics.

Main Methods:

• Full complex field measurements of individual harmonics (23-29) in HHG vortex beams.
• Application of spectrally resolved ptychographic wavefront sensing for high-resolution amplitude and phase retrieval.
• Comparison of experimental measurements with numerical simulations to analyze beam propagation and OAM content.

Main Results:

• High-resolution amplitude and phase profiles for multiple harmonics were retrieved in parallel.
• The study quantified the impact of generation conditions and drive laser aberrations on the generated vortex fields.
• It was found that multimodal vortex beam content significantly affects focal region propagation and field distributions.

Conclusions:

• Accurate multiwavelength reconstruction of HHG vortex beams is achievable.
• Understanding beam propagation and multimodal content is crucial for controlling OAM beam characteristics.
• This analysis facilitates the prediction and generation of attosecond pulse trains and light springs under realistic conditions.