Terahertz wave generation in ripple density plasma assisted by frequency chirped laser pulses

The effect of frequency chirp on the generated terahertz (THz) wave by the interaction between intense laser pulses and rippled density plasma is investigated theoretically. The beating lasers produce a nonlinear ponderomotive force due to their oscillatory motion. This force drives a nonlinear current, at beat frequency which produces the THz radiation. The influences of the density ripple and chirp frequency on the optimization process of THz field amplitude is investigated numerically. A linear frequency chirp increases the duration of nonlinear interaction of laser pulse with plasma electrons and hence, enforces the interaction for longer duration. The exact phase matching condition can be achieved for an optimized value of ripple wave number, which further provides the additional momentum helps to obtain a significant gain in output yield. Our numerical simulations reveal that there is a significant enhancement in the THz field strength for optimized value of chirp parameter and density ripple. (author)