Plasma effects on harmonic spectra generated from moderately relativistic laser-plasma interactions

Area of Science:

• Plasma physics
• Laser-plasma interactions
• Nonlinear optics

Background:

• Intense laser light interacting with plasma can generate energetic electrons via Brunel absorption.
• These energetic electrons excite plasma oscillations, which can influence the emitted radiation spectrum.
• The plasma-vacuum interface plays a crucial role in the generation of plasma line emission.

Purpose of the Study:

• To investigate how plasma oscillations affect high harmonic generation (HHG) and plasma line emission (PLE).
• To characterize the dependencies of HHG and PLE on various plasma and laser parameters.
• To understand the underlying physics of laser-plasma interactions at high electron densities.

Main Methods:

• Particle-in-cell (PIC) simulations were employed to model laser-plasma interactions.
• Simulations covered a range of plasma densities, laser intensities, pulse shapes, and pulse lengths.
• Analysis focused on the resulting electron flux, plasma oscillations, harmonic spectra, and PLE.

Main Results:

• Brunel absorption of intense p-polarized laser light creates fast electrons, driving plasma oscillations.
• Plasma oscillations modulate the high harmonic spectrum at the plasma frequency (ωp).
• Coupling with the plasma-vacuum interface generates PLE at ωp and its harmonics.

Conclusions:

• The generation of HHG and PLE is sensitive to plasma and laser parameters.
• Understanding these dependencies is crucial for controlling and optimizing laser-plasma interactions.
• PIC simulations provide a powerful tool for studying these complex phenomena.