A survey on the mechanisms of powerful terahertz (THz) radiation from laser plasmas is presented. Firstly, an analytical model is described, showing that a transverse net current formed in a plasma can be converted into THz radiations at the plasma oscillation frequency. This theory is applied to explain THz generation in a gas driven by two-color laser pulses. It is also applied to THz generation in a tenuous plasma driven by a chirped laser pulse, a few-cycle laser pulse, a DC/AC bias electric field. These are well verified by particle-in-cell simulations, demonstrating that THz radiations produced in these approaches are nearly single-cycles and linear polarized. In the chirped laser scheme and the few-cycle laser scheme, THz radiations with the peak field strength of tens of MV/cm and the peak power of gigawatt can be achieved with the incident laser intensity less than 10<sup>17</sup> W/cm<sup>2</sup>.
© 2011 Chinese Optics Letters
(260.5210) Physical optics : Photoionization
(320.7120) Ultrafast optics : Ultrafast phenomena
(350.5400) Other areas of optics : Plasmas
(350.5610) Other areas of optics : Radiation
(300.6495) Spectroscopy : Spectroscopy, teraherz
Weimin Wang, Zhengming Sheng, Yutong Li, Liming Chen, Quanli Dong, Xin Lu, Jinglong Ma, and Jie Zhang, "Studies on the mechanisms of powerful terahertz radiations from laser plasmas (Invited Paper)," Chin. Opt. Lett. 9, 110002- (2011)