Terahertz Generation through Photon Deceleration of Long-Wavelength Infrared Laser Pulses in Plasma

Efficient terahertz (THz) generation with high field amplitude and pulse energy is studied through the interaction of a single-color long-wavelength infrared (LWIR) laser pulse with gaseous targets.

Particle-In-Cell (PIC) simulations are performed to investigate the underlying mechanism and analyze the properties of the emitted THz radiation.

The results reveal that THz pulses are generated via photon deceleration of the LWIR laser, driven by enhanced electron density accumulation at the pulse front in the self-modulated wakefield regime.

The influence of key parameters, including target density, laser intensity, and propagation length, on nonlinear laser modulation and the resulting THz generation efficiency is analyzed.

Important scalings governing the laser-to-THz energy conversion efficiency are identified from PIC simulations and validated through theoretical analysis.

The study demonstrates a laser-to-THz energy conversion efficiency of approximately $4\%$, significantly exceeding previously reported values.

The field amplitude of the emitted THz pulses is found to be on the order of 100 GV/m, with a pulse energy of approximately 50 mJ for the laser parameters considered in this work.

The findings of this study provide valuable insights for the development of next-generation high-energy THz sources.