Energy absorption in the laser-QED regime.

Area of Science:

• High-intensity laser-matter interactions
• Quantum electrodynamics (QED)
• Plasma physics

Background:

• Non-ponderomotive absorption is crucial at high laser intensities.
• Understanding electron energy dynamics is key to exploring new physics regimes.
• The Breit-Wheeler process is a fundamental QED phenomenon involving pair production.

Purpose of the Study:

• To theoretically and numerically investigate non-ponderomotive absorption at QED-relevant laser intensities.
• To identify a unique signature for the onset of pair production in high-intensity laser experiments.
• To explore the transition in fast electron energy dependence with increasing laser energy.

Main Methods:

• Theoretical analysis of laser-plasma interactions.
• Numerical simulations using QED-inclusive particle-in-cell (PIC) codes.
• Extensive simulation campaign to cover a range of laser parameters.

Main Results:

• A predicted regime change in fast electron energy dependence on laser energy.
• Numerical verification of this regime change coinciding with Breit-Wheeler pair production.
• Observation of a dramatic power law shift indicating a significant physical transition.

Conclusions:

• The identified regime change serves as a potential unambiguous signature for entering the QED regime.
• Future multi-petawatt laser facilities can use this signature to confirm QED effects.
• This finding advances the experimental search for QED phenomena in laboratory settings.