Terahertz generation by beating of two chirped pulse lasers in spatially periodic density plasma

The present paper reports on the combined influence of the chirp characteristics of pump pulses and spatially periodic density (density ripple) plasma, on terahertz (THz) radiation generation, by beating of two chirped pulses. The beating lasers exert a nonlinear ponderomotive force along the z-direction. A self-consistent field is generated due to the nonlinear oscillations of plasma electrons; as a result of these linear and nonlinear forces the plasma electrons attain an oscillatory velocity that couples with the density ripple to generate a stronger transient transverse current, driving THz radiation. The importance of chirp parameter, amplitude and periodicity of density structure are discussed for emitted THz radiation. Our numerical simulations disclose that the variation of the chirp frequency parameter and ripple amplitude have considerable roles in improving the nonlinear oscillating current. By optimizing the chirp parameter and amplitude of the density ripple, a notable change in the magnitude of the terahertz field amplitude is found. The present paper maybe useful for broadband THz pulses, for use in plasma diagnostics and time-domain spectroscopy.