Calculation of high-order harmonic generation in laser-produced lithium plasma

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Optics
• Nonlinear Optics

Background:

• High-order harmonic generation (HHG) is a crucial nonlinear optical process.
• The Lewenstein model is a widely accepted theoretical framework for describing HHG.
• Previous experimental studies on HHG in lithium plasma provide a basis for theoretical validation.

Purpose of the Study:

• To perform detailed calculations of HHG spectra for lithium (Li) and helium (He) atoms and Li ions.
• To validate the Lewenstein model against experimental HHG data in Li plasma.
• To investigate the influence of ionization potential on HHG cutoff extension.

Main Methods:

• Utilized the Lewenstein model for theoretical calculations of HHG spectra.
• Performed numerical simulations of HHG in Li, Li+, and He.
• Compared simulation results with experimental data for Li plasma.

Main Results:

• The model accurately describes the HHG experiment in Li plasma.
• Simulated cutoff for Li atoms corresponds to 3.5×10^14 W/cm^2 laser intensity.
• Li+ ions do not contribute to the HHG plateau at typical intensities; they contribute only at very high intensities.
• Higher ionization potential does not guarantee an extended HHG cutoff.

Conclusions:

• The Lewenstein model is a reliable tool for simulating HHG spectra.
• Experimental uncertainties can explain discrepancies between simulated and experimental cutoff values.
• Ion species and ionization potential play complex roles in HHG, not always leading to expected extensions of the cutoff.