ABSTRACT
The interaction of an intense laser pulse with a gaseous medium allows tunnel ionization of the atoms under certain conditions and generates plasma that can withstand high electric fields and a higher damage limit. The generation of efficient and strong terahertz (THz) radiation by this type of laser-plasma interaction is discussed in this chapter. The main focus has been on the laser beating mechanism, where there is a slight difference between the frequencies and the wavenumbers of the two incident laser beams with the same electric field. Nonlinear ponderomotive force exerted on the electrons perturbs the electron density and generates an oscillatory current in the plasma. The detailed description of this generated nonlinear current oscillating at beating frequency is given; this current acts as a source for the emission of THz radiation. The effect of laser and plasma parameters (such as laser's spatial profile, beam width, and plasma density) on this emitted THz field is discussed in spatially modulated plasma density. The role of an external magnetic field in terms of tuning the frequency and power of the emitted THz radiation is deliberated. Finally, the control of THz polarization is discussed.
