Using a well-developed transient photocurrent model, we combine theoretical and numerical studies on the production of terahertz (THz) radiation in laser-induced air plasma. Air molecules are excited and then ionized by the laser-pulses mixing the fundamental and second harmonic fields. As a result, a non-vanishing directional photoelectron current emerges, radiating the THz pulse wave. We mainly discuss the influences of optical wavelength on THz radiation in five different cases. Results show that the fundamental-pulse width (50 fs), energy, and relative phase between two pulses are invariant. When the laser wavelength (from 400 nm to 1.25 \mu m) becomes longer, the emitted THz fields are significantly enhanced, with a linear dependence on the optical wavelength.
© 2013 Chinese Optics Letters
(140.3440) Lasers and laser optics : Laser-induced breakdown
(190.7110) Nonlinear optics : Ultrafast nonlinear optics
(320.2250) Ultrafast optics : Femtosecond phenomena
(260.7120) Physical optics : Ultrafast phenomena
Lasers and Laser Optics
Siqing Wu, Jinsong Liu, Shenglie Wang, and Yanan Zeng, "Influence of optical wavelength on terahertz radiation from laser-induced air plasma," Chin. Opt. Lett. 11, 101402- (2013)