Powerful laser-produced quasi-half-cycle THz pulses.

Area of Science:

• Physics
• Electromagnetism
• Plasma Physics

Background:

• Transition radiation is a key phenomenon in laser-plasma interactions.
• Terahertz (THz) radiation generation and characterization are crucial for various applications.
• Understanding the near-field behavior of THz pulses is essential for advanced studies.

Purpose of the Study:

• To develop a 3D analytical solution for terahertz (THz) half-cycle electromagnetic wave transition radiation pulses.
• To describe the generation and propagation of THz transition radiation from relativistic electron bunches interacting with targets.
• To complement existing theories and enable detailed analysis of THz wave characteristics, including near-field effects.

Main Methods:

• Maxwell equations-based 3D-analytical solution.
• Finite-difference time-domain (FDTD) simulations for wider spatial domain analysis.
• Comparison with particle-in-cell (PIC) approaches.

Main Results:

• A comprehensive analytical solution for THz half-cycle transition radiation pulses was derived.
• The solution accurately describes THz wave propagation from the target surface into free space, including the near-field zone.
• 3D simulations validated the analytical model and extended the analysis to a broader spatial domain.
• The study illuminates the interference between electron bunch fields and broadband transition radiation fields.

Conclusions:

• The developed analytical solution provides a fundamental understanding of THz transition radiation from laser-driven electron bunches.
• This work enhances the theory of laser-initiated transition radiation, particularly for near-field characterization.
• The findings may guide future experiments investigating intense half-cycle THz radiation in laser-plasma interactions.