Multi-millijoule terahertz emission from laser-wakefield-accelerated electrons.

Area of Science:

• Plasma Physics
• Laser-Induced Phenomena
• Terahertz (THz) Science

Background:

• Laser-wakefield acceleration (LWFA) is a method for generating high-energy electron beams.
• High-power terahertz (THz) radiation can be a byproduct of LWFA processes.
• Understanding THz generation in LWFA is crucial for advanced applications.

Purpose of the Study:

• To investigate the generation of high-power THz radiation from gas jets irradiated by 100-TW laser pulses.
• To characterize the spectral, polarization, and energy properties of the emitted THz radiation.
• To elucidate the underlying physical mechanisms responsible for THz emission in LWFA.

Main Methods:

• Experimental setup involving a 100-TW class laser system and a gas jet target.
• Characterization of emitted THz radiation using spectroscopy, polarimetry, and energy measurements.
• Theoretical modeling including analytic calculations and particle-in-cell (PIC) simulations.

Main Results:

• Observation of high-power THz radiation emission.
• Generation of over 4 mJ of THz energy at <10 THz using a nitrogen target.
• Achieved a laser-to-THz conversion efficiency of approximately 0.15%.
• Demonstrated dependence of THz properties on electron bunch energy, charge, and gas target conditions.

Conclusions:

• The study provides significant insights into the generation of intense THz radiation in LWFA.
• The hypothesized mechanism involves plasma electrons accelerated by laser ponderomotive force and plasma wakefields.
• Further understanding of THz generation can enable novel applications in various scientific fields.