External static electric field assisted THz radiation generation via optical rectification of secant hyperbolic laser pulse in a plasma

In collisionless plasma, the function of an externally imposed static electric field has been investigated for facilitating the generation of high-power terahertz (THz) radiation. A nonlinear transient current density occurs at THz radiation frequency due to the optical rectification of high-power laser pulse having secant hyperbolic temporal intensity profile. This transient current driving a THz radiation is found to be strongly depended on the pulse width of laser, electron plasma frequency, and externally applied electric field. The effect of mismatched phase between the generated THz wave and laser has also been studied. Numerical simulations show that the strength of THz amplitude initially increases with propagation distance and then decreases.