High-order harmonic generation from ions in a capillary discharge

Area of Science:

• Laser Physics
• Plasma Physics
• Quantum Optics

Background:

• High-order harmonic generation (HHG) is a key process for producing extreme ultraviolet (XUV) and soft X-ray radiation.
• Traditional HHG in gases faces limitations due to phase-mismatch and ionization, restricting achievable photon energies and flux.
• Utilizing plasma as a generation medium offers potential to overcome these limitations.

Purpose of the Study:

• To demonstrate significant extension of the high-order harmonic cutoff using a fully-ionized capillary discharge plasma.
• To investigate the impact of plasma on laser propagation and energy loss.
• To enhance harmonic flux and photon energies for potential applications.

Main Methods:

• Generation of high-order harmonics in a fully-ionized capillary discharge plasma.
• Comparison of harmonic generation in plasma versus hollow waveguides.
• Characterization of generated photon energies and flux.

Main Results:

• Achieved significant extension of the high-order harmonic cutoff, generating photon energies up to 150 eV from xenon ions.
• Observed a dramatic reduction in ionization-induced defocusing and laser energy loss.
• Demonstrated enhancement of harmonic flux by nearly 2 orders of magnitude around 90 eV compared to hollow waveguides.

Conclusions:

• Fully-ionized capillary discharge plasma is an effective medium for extending high-order harmonic generation.
• This approach significantly enhances photon energies and flux, enabling shorter wavelength generation.
• Plasma-based HHG shows great promise for efficient generation of XUV and soft X-ray radiation using ions.