Efficient terahertz radiation generation from air plasma with mid- and near-infrared three-color femtosecond pulses

Area of Science:

• Physics
• Optics
• Laser Science

Background:

• Terahertz (THz) radiation generation is crucial for various scientific and technological applications.
• Conventional methods often rely on two-color laser fields, limiting achievable THz pulse energies.

Purpose of the Study:

• To investigate the enhancement of THz radiation generation using a three-color femtosecond laser field.
• To explore the influence of relative phase control and incident pulse energy on THz output.
• To understand the underlying mechanisms responsible for THz energy enhancement.

Main Methods:

• Generation of a three-color femtosecond field (near- and mid-infrared) to drive air plasma.
• Utilized an inline optical setup for precise control over pulse generation and relative phase.
• Employed analytical and numerical modeling based on the plasma current model.

Main Results:

• Achieved up to a 6-fold enhancement in THz pulse energy compared to two-color schemes.
• Observed elliptical polarization for the enhanced THz pulse and harmonic components.
• Reached a maximum THz pulse energy of 39.4 µJ with a 1% conversion efficiency using 3.9 µm driving pulses.

Conclusions:

• The addition of a third harmonic to the driving laser field introduces new ionization wave mixing channels, significantly enhancing THz generation.
• The developed three-color excitation scheme offers a more efficient pathway for producing high-energy THz radiation.
• The findings provide valuable insights into controlling and optimizing THz radiation generation for advanced applications.