Materials science

Femtosecond pulse shaping

Laser

Physics

Optics

Ultrafast optics

Terahertz radiation

Terahertz spectroscopy and technology

Filamentation

Femtosecond

Optoelectronics

Photonics Research

In this work, it has been demonstrated that in order to fully understand the terahertz (THz) pulse generation process during femtosecond laser filamentation, the interaction between THz wave and air plasma has to be taken into account. This interaction is mainly associated with the spatial confinement of the THz pulse by the plasma column, which could be described by the one-dimensional negative dielectric (1DND) waveguide model. By combining the 1DND model with the conventional four-wave mixing (4WM) and photocurrent (PC) models, the variation of THz spectral amplitude and width obtained in experiments could be better understood. Finally, a three-step procedure, with 1DND bridging 4WM and PC processes, has been established for the first time to describe the underlying mechanism of THz radiation from plasma sources.

Clue to a thorough understanding of terahertz pulse generation by femtosecond laser filamentation