Terahertz Generation by Intense Femtosecond Gaussian Laser Pulse in Ripple Density Plasma

Terahertz (THz) generation by an intense femtosecond Gaussian laser pulse (Gaussian in space and time) in rippled density plasma has been investigated in the relativistic regime. A component of ponderomotive force is exerted on electrons due to the variation in intensity in the direction transverse to the laser propagation that results in a transient current driving a radiation. If the pulsewidth of the laser is suitably chosen, the frequency of this generated radiation falls in the THz region. The necessary condition for phase matching is provided by the density ripple. The effects of transient focusing of the laser pulse on the generated THz amplitude have also been studied. Numerical simulations show a significant increase in the THz field strength with occurrences of relativistic ponderomotive self-focusing.