Above threshold ionization in tightly focused, strongly relativistic laser fields

Area of Science:

• Plasma Physics
• Laser-Matter Interactions
• High-Intensity Laser Physics

Background:

• Electron ionization dynamics are crucial for understanding laser-matter interactions.
• Previous studies focused on sub- and near-relativistic laser intensities (<10^19 W/cm^2).
• The behavior of electrons under ultra-relativistic conditions (>10^20 W/cm^2) requires further investigation.

Purpose of the Study:

• To investigate the dynamics of electrons ionized from high charge states by ultra-intense lasers.
• To understand the influence of laser intensity on electron trajectories and energy gain.
• To compare electron dynamics in ultra-relativistic versus lower-intensity laser fields.

Main Methods:

• Theoretical analysis of electron motion under intense laser fields.
• Monte Carlo simulations to model electron trajectories and energy.
• Focus on the role of magnetic (vxB) and electric fields.

Main Results:

• At intensities >10^20 W/cm^2, vxB forces propel electrons parallel to laser propagation.
• Electrons gain significant energy by staying in phase with the laser field over extended distances.
• Ultra-relativistic electron dynamics are strongly affected by longitudinal electric fields near the laser focus, differing from lower-intensity regimes.

Conclusions:

• Electron dynamics under ultra-intense laser fields are distinct from those at lower intensities.
• Longitudinal electric fields play a critical role in shaping electron trajectories and energy gain in the ultra-relativistic regime.
• Understanding these dynamics is key for applications involving high-intensity laser-plasma interactions.