Plasma high-order-harmonic generation from ultraintense laser pulses.

Area of Science:

• Plasma physics
• Nonlinear optics
• Attosecond science

Background:

• High-order harmonic generation (HHG) in plasmas is a key process for producing coherent extreme ultraviolet (XUV) and attosecond radiation.
• Understanding the complex plasma dynamics, including ion motion and relativistic effects, is crucial for optimizing HHG.

Purpose of the Study:

• To investigate the influence of ion motion, electron-ion collisions, and radiation reaction force on plasma high-order harmonic generation.
• To identify optimal parameters for generating intense single attosecond pulses and coherent XUV radiation.

Main Methods:

• Numerical simulations incorporating plasma dynamics, laser radiation pressure, hole-boring effect, electron-ion collisions, and classical radiation reaction force.
• Analysis of harmonic spectra for frequency shifting and broadening.

Main Results:

• Laser radiation pressure drives ion motion, causing significant frequency shifting and broadening of harmonic spectra.
• The classical radiation reaction force partially counteracts the spectral broadening induced by ion motion.
• Parameter maps are developed to identify optimal conditions for generating specific harmonic characteristics.

Conclusions:

• Ion motion and radiation reaction are critical factors in plasma HHG, influencing spectral properties.
• The findings provide a pathway for optimizing the generation of intense attosecond pulses and coherent XUV radiation.
• The presented parameter maps serve as a guide for experimentalists aiming to control and enhance HHG processes.