Terahertz radiation from oscillating electrons in laser-induced wake fields

Area of Science:

• Plasma Physics
• Laser-Plasma Interactions
• Terahertz (THz) Science

Background:

• Terahertz (THz) radiation generation is crucial for various scientific and technological applications.
• Femtosecond (fs) laser-induced wake fields in plasma offer a promising route for strong THz emission.

Purpose of the Study:

• To investigate the interaction of fs-laser pulses with low-density plasma layers for THz generation.
• To analyze the spatial and temporal characteristics of THz electron currents and radiation.
• To determine optimal conditions for wake-field excitation and THz emission.

Main Methods:

• Detailed numerical simulations of fs-laser pulse interaction with a low-density plasma layer.
• Analysis of electron current evolution and spatial distribution.
• Calculation of THz radiation intensity distribution.

Main Results:

• Identified key laser parameters (intensity, pulse width) and plasma parameters (density) influencing THz generation.
• Achieved THz radiation peaked at 6.4 THz with 900 fs duration and 9% bandwidth in a plasma of density 5x10^17 cm^-3.
• Demonstrated that maximum THz intensity scales as n(0)^3 * a(0)^4 for resonant wake-field excitation.

Conclusions:

• Femtosecond laser-plasma interactions provide an effective method for generating strong THz radiation.
• Optimization of laser and plasma parameters is critical for maximizing THz emission efficiency.
• The scaling law provides a predictive tool for designing future THz sources.